Kinh Te Moi Truong Bai Tap

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Environmental Economics Teachers Manual 2005

KINH T MI TRNG

CU HI, BI TP V TR LI

B sung cho ti liu hng dn ging dy

dnh cho

Chng trnh i hc I HC VIT NAM

Thng 8, 2005 Chng trnh Kinh t v Mi trng ng Nam

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BI 1: GII THIU

CH : Kinh t Mi trng l g?

Ngun: F & O (2005) and F, O, & F (2002)

Cu hi 1. Ti sao thu xng du to khuyn khch gim thi kh t xe t nhiu hn so vi thu s hu/s dng xe hng nm?

Gii p:

Cu tr li tu thuc vo mc thu xng du so vi thu s hu xe. Thu xng du nhm vo ba yu t ca gim pht thi [ l a)s xe tham gia giao thng; b) qung ng mi xe chy; v c) lng kh thi mi dm xe chy].

Mt khc, thu hng nm ch nh hng quyt nh c nn tng s xe tham gia giao thng (bao gm c mua hoc thi khng tham gia giao thng). Tuy nhin, nu thu xe l cao rt t ngi a xe tham gia giao thng, khi kh thi s gim tng ng vi thu nhin liu thp v ngi ta ch li xe mt lng ti a no mi ngy. Bi v thu xe cao nh vy l khng kh thi v mt chnh tr (l do bnh ng), v vy thu xng du s c nh hng gim thi ln hn.

Cu hi 2. Nhng yu t no nh hng nhng nh i (trade-offs) c minh ho ng gii hn cong kh nng sn xut? Chnh sch mi trng c th nh hng nhng nh i ny nh th no?

Gii p:

C kh nng cng ngh ca nn kinh t v iu kin sinh thi c th nh hng s nh i dc theo ng cong kh nng sn xut. nh hng c hi i vi mi trng xut hin l do nn kinh t s dng dng ti nguyn thin nhin v do cht thi ca qu trnh sn xut v tiu dng. i mi cng ngh lm gim lng u vo hoc cht thi cho mi n v u ra c th lm dch chuyn ng cong kh nng sn xut ln pha trn nhiu hng ho c sn xut hn cho mi n v cht lng mi trng. iu ny l ng trong trng hp ti ch v ti s dng cng ngh.

Chnh sch cng c th nh hng nhng nh i bng cch khuyn khch ngi tiu dng v cc hng thc hin nghin cu v pht trin (R&D) v p dng cng ngh cho php gim nh hng mi trng cho mi n v u ra. Chnh ph cng c th thc hin R&D v cung cp thng tin v cc cng ngh sn c nhng ng cong kh nng sn xut tim nng c th c thc hin (v d tim nng t C ch Pht trin sch cho c nc pht trin v ang pht trin).

Cui cng, vai tr ca vic ci thin sinh thi gim thiu nhng nh i c th c tho lun. tng l cc c th trong mt cn bng sinh thi to ra cht thi v s dng cc u vo duy tr s hot ng ca h sinh thi nh l mt tng th.

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Cu hi 3. Hy ch r i mi cng ngh cho php cc hng sn xut hng ho v dch v vi nhim t hn nh th no? S dng th ng cong kh nng sn xut gii thch.

Gii p:

Nhiu hng ho hn c th sn xut vi mi n v cht lng mi trng ng cong gii hn kh nng sn xut dch chuyn (xem S 1.1 trong sch do Fill and Olewiler bin son) ln pha trn, vi mc cht lng mi trng khng thay i. Cht lng mi trng tng ln hoc gim xung tu thuc vo ng bng quan ca cng ng/x hi (CIC). Gi s cng ngh tng ln cho php ngi ta c nhiu con hn. Mc tiu dnh bnh qun u ngi gim thp s lm tng gi tr ca hng ho so vi vi cht lng mi trng lm cho ng bng quan ca cng ng tr nn bt hn th hin sn lng cn bin cao hn trong nh i cht lng mi trng cho hng ho. Trong trng hp ny, cht lng mi trng b gim thp so vi trc thay i cng ngh. l nhng g din ra trong sut lch s. Mt khc, nu ngi ta giu hn mc trung bnh, h c th c c gi tr tng ln t cht lng mi trng so vi tiu dng. Trong trng hp ny CIC s tr nn dc hn phn nh sn lng cn bin thp hn nh i cht lng mi trng cho hng ho.

Cu hi 4. Anh/ch hy cho bit bt k khuyn khch no c tc ng nht qun vi tnh bn vng? Anh/ch hy cho bit bt k khuyn khch no c tc ng ngc li? Lm th no c th thay i nhng khuyn khch c tc ng ngc li ?

Gii p:

Trc ht cn phi tr li nhng hnh vi no th nht qun vi pht trin bn vng. Trong nhiu trng hp, y l vn tranh ci. V d, ngi ta tin tng rng mi lc mi ni ti ch nhiu hn l iu tt nu mun t c bn vng bi v n gim c lng cht thi v mc khai thc ti nguyn nguyn thu. iu ny khng phi khi no cng ng. Ti ch s dng ti nguyn thin nhin v nng lng. Nhng chuyn xe hi ca cc c nhn ch vi mc tiu duy nht l a cht thi n cc phng tin ti ch c th gy nn thit hi mi trng ln hn do t chy nhin liu so vi thit hi phng trnh. T vin cnh thay i kh hu, gim t chy nhin liu t lng t chc chn lun lun lm tng trin vng bn vng. i li bng thuyn, tu la, hoc xe but, ch khng phi bng xe hi c nhn, nhn chung l nht qun vi tnh bn vng hn. C cu khuyn khch chn la phng tin giao thng thay i theo theo tng quc gia v iu kin a phng. Thay i khuyn khch theo hng gim s dng xe hi c nhn v my bay l mt vn ca chnh sch chnh ph. Xut pht t thc t phn ln ngi cc nc cng nghip pht trin c thi quen s dng xe hi t nhn v my bay, v h thng cai tr c tnh dn ch hin c cc x hi , trin vng thay i khuyn khch theo hng l c l khng ln. C th k n l vic thi rc, mua sn phm vi nhiu bao b so vi khng bao b, ti thiu ho s dng nc ca cc h gia nh.

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BI 2: MI QUAN H GIA MI TRNG V NN KINH T V TNG QUAN V NHNG VN TI NGUYN, MI TRNG

CH 1: Mi quan h gia mi trng v nn kinh t

Ngun: F & O, Chng 2; v F, O, & F 2002

Cu hi 1: Tng trng dn s nh hng nh th no n s cn bng ca cc dng trong S 2.1?

Gii p:

Tng trng dn s ph v quan h trc tip gia khi lng vt cht v nng lng c a vo h thng v khi lng pht thi. Tng trng c ngha mt phn ca ti nguyn tch lu trong dn s ang tng. iu ny cng ng cho h thng vt cht, nhu s tch t ca ti sn vt cht. Chng no tng trng vn tip tc s khc nhau gia u vo v u ra vn tn ti.

Cu hi 2: Nu tt c cc hng ho c th thay i ngay tc th (overnight) chng c th tn ti lu gp i so vi trc y, iu ny lm thay i cc dng lun chuyn trong S 2.1 nh th no?

Gii p:

iu ny s lm gim rt ln lng cht thi bi v n lm gim mt cch ng k lng ti nguyn duy tr cc hot ng kinh t mt mc nht nh. Thc cht, l s gim Rp, theo thut ng ca m hnh. Tt nhin, iu ny khng ph v cn bng di hn ca u vo v cht thi. Nhng lng ti nguyn cn thit phc v cho mt mc hot ng kinh t nht nh cng nh lng cht thi s gim i mt na.

Cu hi 3: Mt lng cht thi c thi vo mt thi im no mt ni no c th l cht gy nhim; nu n c thi mt thi im khc hoc mt ni khc th n c th khng to thnh cht gy nhim. Ti sao iu ny li ng?

Gii p: Cu hi ny nhm nhn mnh rng khng ch c loi cht thi l quan trng, m c khi no v u n c thi. Cht nhim l ci g gy thit hi, v mc thit hi ph thuc vo kh nng hp ph/ng ho ca mi trng cng nh dn s v ti nguyn sinh thi tip xc vi cht thi. V d: ting n t sn bay gn thnh ph v cng mc ting n nh vy nhng sn bay xa; cht thi do khng kh mang theo trong thi gian hon nghch nhit so vi nhng ngy lng gi.

Cu hi 4: Ti sao nhng cht gy nhim tch lu tn ti lu li kh qun l hn cht gy nhim khng tch lu tn ti trong thi gian ngn?

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Gii p:

Cht gy nhim khng tch lu, tn ti trong thi gian ngn gy thit hi v bin mt, cho nn nu chng ta mun gim thit hi chng ta ch cn gim mc thi hin thi. Nhng cht thi tch lu tn ti y gy thit hi trong tng lai, v vy cn thy trc qun l thit hi, v iu thng kh t c. iu l hc ba v vic nghin cu tr nn kh khn hn - phi d bo nh hng lu di trong tng lai; v n hc ba v ngi ta thng thc hin chit khu theo thi gian.

Cu hi 5. Gi s chng ta quan st thy pht thi cht nhim gim xung nhng cht lng mi trng khng tng ln c th gii thch iu ny nh th no?

Gii p:

Mt s nguyn nhn c lit k: 1) mc pht thi c th gim nhng cht nhim c tnh tch lu nn lng cht nhim tng ln. cht nhim gim xung, tc phn hu hoc hp th ca mi trng t nhin phi ln hn tc thi cht nhim, 2) Trc khi gim thi cht lng mi trng c th b suy thoi n ni mc thi thp cng gy thit hai nh mc thi cao gy nn, 3) C th c s tr gia pht thi v thit hi mi trng do tnh phc tp ca h sinh thi. H sinh thi c th t mc thit hi ngng v sau n hu hoi mt cch nhanh chng. 4) Thit hi mi trng c th do nh hng kt hp t nhng cht gy nhim khc nhau. V d, cc nh khoa hc bo co rng mc kh CO2 cao c th lm tng tc hnh thnh cc l hng zn, 5)Mc du pht thi mt cht gy nhim l thp hn, cc hng c th tm gii php thay th, nhng gii php ny cng gy thit hi.

Cu hi 6: Vic nghin cu cc vn ti nguyn thin nhin cn phi tha nhn tm quan trng v k thut/khoa hc, kinh t, v chnh tr x hi. Hy gii thch ( Trch dn t Perman, Ma, McGilvray, and Common, 2003)

Gii p:

Trch dn ny gi rng c c li gii p y v cht ch v vn ti nguyn thin nhin cn p dng phng php a ngnh. Tuy nhin, trong nghin cu vn mi trng, nh kinh t s sm pht hin ra rng s tc ng qua li gia h thng kinh t v mi trng i hi cn phi a vo cc ni dung, phng php ca khoa hc t nhin, tri t v s sng. Hn th na, vn phn phi thu nhp v ca ci trong nc v quc t v qua thi gian, v vn thit lp v thc hin chnh sch m bo chc chn rng nhng quan tm v x hi chnh tr s lun lun l c ngha.

BI 3: NGUYN NHN CA CC VN MI TRNG

CH : Nguyn nhn ch yu ca cc vn mi trng trn th gii l g?

Ngun: Field & Olewiler, trang 84, v Forsdyke, Field v Olewiler, 2002

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Bi tp 1. Di y l mt phn ng cu ca ba c nhn v cht lng khng kh ca vng ln cn. Cht lng khng kh (ch mang gi tr nguyn) c o bng g/m3 (micrograms kh SO2 c trong mt mt khi kh). Nu chi ph cn bin gim kh SO2 vng xung quanh l 40 $ cho mi g/m3, mc cht lng khng kh hiu qu x hi l g, gi s rng x hi trong trng hp ny ch bao gm ba ngi ny.

Lng cu Chi ph x l kh SO2 ( la/microgram/m3) A B C

60 50 40 30 20 10 0

1.400 1.300 1.200 1.100 1.000 900 800

1.200 1.100 1.000 900 800 700 600

1.500 1.400 1.300 1.200 1.100 1.000 900

Gii p:

y l cu hi sinh vin thc hnh tm ng cu tng ca hng cng cng. Trc honh o mc cht lng khng kh tng ln theo chiu sang phi, c ngha gim kh SO2 trong khng kh. Trong trng hp ny ng tng cu c xc nh tng theo chiu dc sn lng chi tr ca c nhn:

g/m3 Tng gi sn lng chi tr cn bin (MWTP) 1200 1100 1000 900 800 700 600

130 100 70 40 20 10 0

ng tng cu khng c xc nh r rng ti mc cao hn 1200 g/m3 ng cu c nhn B ch c bit n mc . Hiu qu t c mc 900 g/m3.

Bi tp 2: i vi bi tp 1, hy chng ming rng mc cht lng khng kh hiu qu x hi s ti a ho li ch rng x hi.

Gii p:

Sinh vin c th chng minh theo hai cch rng mc cht lng khng kh hiu qu x hi s ti a ho li ch rng x hi. S dng phng php 1, i vi mc cht lng khng kh trn 900, MWTP (li ch cn bin x hi) gim kh SO2 vt qu chi ph x l cn bin x hi. V vy, nu cht lng khng kh c ci thin, mc gim thit hi phi vt qu chi ph c c li ch rng x hi tng thm. Ngc li, nu cht

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lng khng kh di mc 900, gi sn lng chi tr cn bin nh hn chi ph x l cn bin(MAC). Bng cch gim cht lng khng khi mt n v, chi ph x l tit kim c s ln hn thit hi gim xung li ch rng tng thm. Thng d x hi khng th tng thm y nu MAC = MD (thit hi cn bin). Phng php th hai v th ng MWTP v MAC v s dng din tch pha di nhng ng ny tnh ton li ch rng x hi. Gi s ch s cht lng khng kh ban u l 1200, gi tr rng tng thm do lm sch n mc cht lng mi trng di y c minh ho sau y.

Ch s cht lng khng kh

Tng WTP Tng chi ph Gi tr rng x hi

7500 1000 900 800 700 600 500 400 300

11500 20000 25500 27500 29000 29500 29500 29500 29500

4000 8000 12000 16000 20000 24000 28000 32000 36000

7500 12000

13500 (MAX) 11500 9000 5500 1500 -2500 -6500

Ngun: Perman, Ma, McGilvray, v Common, 2003

Cu hi 1. Quan h gia hng ho cng cng v ti nguyn t do tip cn l g?

Gii p:

Khi con ngi s dng qu mc ti nguyn t do tip cn, s gn gi ti nguyn ca mt ngi s dng s em li li ch cho tt c cc ngi s dng khc; s gn gi ca mt c nhn, ni cch khc, l mt hng ho cng cng, cung hng ho cng cng khng (v n theo) dn n s dng ti nguyn qu mc.

Cu hi 2. Mt s hng ha c v l hng cng cng, nh sng radio, dch v nh n, v thm ch dch v cng an v v sinh, c th c cung cp bi cc hng t nhn. Ti sao li nh vy? C nhng khc nhau gia nhng hng ho cng cng ny vi dch v mi trng khng? Nu c, nhng khc nhau l g?

Gii p:

Hng t nhn c th khng cung cp hng ho cng cng dn n cn c hnh ng tp th. Chnh ph hnh ng nh l ngi phc v cng chng. Trong mt s trng hp, chnh ph c th hp ng cung cp dch v hng ho cng cng cho cc hng t nhn. Ti sao nh nc c th hp ng mt s dch v ny m khng hp ng i vi dch v khc? Li gii p ph thuc vo bn cht ca hng ho hoc dch v cng cng. Nu n c th sn xut v hp l t nhn c th cung cp. Chnh ph c th tr tin v gim st vic cung cp dch v. V d, mt nh thu t nhn c chnh qun thnh ph thu cung cp dch v mi trng nh thu gom rc thi v dch v v sinh. Mt khc, quy

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nh mi trng l cn thit m bo rng mc tiu cht lng mi trng c p ng i vi phn ln cc hng ho cng cng nh cht lng khng kh. Cc hng t nhn khng c quyn lc iu tit cc hng khc v hnh ng ca ngi tiu dng.

Cu hi 3: Ti sao chng ta phi quan tm t c hiu qu x hi?

Gii p:

Hiu qu x hi (SE) cung cp phng php nh gi x hi hot ng tt nh th no v liu thay i v chnh sch c t c nhng ci thin hay khng. SE l thc s ph hp trong kinh t mi trng bi v n xc nh gi tr ca cc tin nghi mi trng khng c gi th trng. Lm nh vy, n thu ht s ch i vi nhng tht bi th trng to ln v quan trng. Trong trng hp phn phi ca ci khng bt bnh ng nhiu, SE c th c iu chnh bng cch gn trng s cho nhng nhm ngi c thu nhp khc nhau (xem di y). Cn nhn mnh rng mc du nhng ngi ra quyt nh c th chn la thc hin phn phi , th trng khng lm c iu . Mc du, hm hu ch ch th hin trt t chn la v mt l thuyt khng th gp li, c l t gic bnh ng iu tt nht chng ta c th lm l tnh ton hu ch ca mi ngi nh nhau.

Cu hi 4: Cc kt qa hiu qu x hi c nht thit cng bng khng? Chng c cn phi nh vy khng?

Gii p:

Phn phi t hiu qu x hi khng nht thit phi cng bng. Nu nh ngi ta c ng c v li ch c nhn v tn tu lm vic tch cc hn da trn nhng n b khc nhau, khi tng sn lng c th cao hn. Mc sn xut cao hn c th dn n thng mi nhiu hn cho nn c nhiu c hi hn chuyn mn ho v v vy c nhiu vic lm trong nn kinh t. V vy, trong mt x hi khng bnh ng nhng ngi ngho nht c th c cuc sng vt cht tt hn trong mt x hi bnh ng. ng c li nhun (n b khng cng bng) c th khuyn khch nghin cu v pht trin cng ngh mi. ng c gim thp chi ph c th lm gim nh hng mi trng bt li v s dng u vo t hn sn xut mi n v sn phm. Mc d mi n v sn phm sn xut to ra t cht thi hn, sn lng nhiu hn lm tng chi ph ngoi vi i vi mi trng (v d Hoa K l quc gia thi nhiu kh CO2 trn th gii). Nu ngi ngho khng kh ln v mt tuyt i v ci bnh ln hn, bi thng c th c thc hin v mt nguyn tc. V d, thu sut cao c th dn n thay i v tr kinh doanh. Hiu qu x hi c th c iu chnh xem xt bnh ng bng cch gn trng s phc li cho cc nhm thu nhp khc nhau. Do , hu ch cn bin ca mt la i vi ngi ngho l cao hn so vi ngi giu, iu ny phn nh MWTP khng ch ph thuc vo li ch m cn ph thuc vo kh nng thanh ton.

Cu hi 5. Tho lun s thch hp v s vn dng khi nim nh hng ngoi vi trong kinh t mi trng.

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Gii p:

Hc thuyt nh hng ngoi vi l mt trong nhng nn tng quan trng ca kinh t mi trng. Chng hn phn ln cc hc thuyt kinh t v nhim c xy dng theo khun kh nh hng ngoi vi. Kinh t mi trng nhm ti ni ho nh hng ngoi vi. V iu ny qun xuyn ton b ch cng c kim sot nhim. Khi nim ny cng rt quan trng trong khc ch khc trong kinh t mi trng v c th xem n trung tm ca nhng tho lun v kinh t mi trng.

Cu hi 6: Cc nh kinh t mi trng xem vn nhim nh l mt loi hin tng nh hng ngoi vi bt li. nh hng ngoi vi xut hin khi quyt nh ca mt ch th nh hng ch th khc mt cch khng c , v khng c bi thng. C phi iu ny c ngha l nu mt ngun nhim, chng hn nh my nng lng bi thng nhng ngi b nh hng bi cht thi, th khi khng c vn nhim?

Gii p:

iu ny ph thuc vo vn nhim c ngha l g. Ni chung, thm ch khi c bi thng, pht thi vn din ra v nhim vn tip tc. Tuy nhin, cc nh kinh t c khuynh hng s dng thut ng vn nhim khng phi hm rng c tn ti nhim mi trng m m t mc nhim mi trng khng hiu qu x hi. Nu thc hin bi thng cho tt c nhng ngi b nh hng bt li v bi thng c thc hin ng n cho nhng c nhn b thit hi v nh my tr bi thng iu chnh hnh vi ca mnh mt cch ti u xem xt cc khon bi thng phi tr, khi tnh trng sau bi thng s t hiu qu kinh t, v nh vy khng phi l vn nhim.

Cu hi 6: Trong khi mt s nh kinh t tranh lun cn thit lp quyn ti sn t nhn bo v mi trng, nhiu ngi quan tm v mi trng cho rng phng php ny khng ph hp. Vn ct yu trong tranh lun l g?

Gii p:

Thit lp quyn ti sn t nhn c th ci thin hiu qu phn phi ti nguyn tnh v ng. Ch s hu ti nguyn s tnh n chi ph c hi cu vic tip cn, hoc khai thc/thu hoch, ti nguyn. Nhng khon chi ph ny s c tnh vo gi bi nhng ngi s dng ti nguyn. y l bi cnh m dng nh xu hng s dng ti nguyn theo thi gian c th ng vi ti u x hi khc vi nhng g c th xy ra khi khng c quyn ti sn. N cng c th dn n phn phi ti nguyn gn vi m hnh bn vng (mc du mt kt qu hiu qu khng nht thit phi l mt kt qu bn vng).

Tuy nhin, d c nhng phn i v mt o c i vic thit lp quyn ti sn t nhn. nhng nn kinh t giu c, nhiu ngi tranh lun phn ln t gi thuyt cho rng vng ni v nhng vng hoang d khc ang v nn c qun l bi tp th cng ng c phn nh kh rng. nhiu ni trn th gii, c tn ti quyn s hu tp th hoc cng cng lu i v ti nguyn nc, bi chn th gia sc, nhng loi c th thu hoch

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hoc nhng g tng t. D thy rng c nhng mu thun tim n gia duy tr truyn thng vn ho v mc tiu hiu qu kinh t.

Ngi ta ni khng c l do ti sao quyn ti sn t nhn cn thit l da vo c nhn. Tt c nhng g cn c l mt tp hp c nh ngha r rng gm nhng ngi c giao quyn ti sn v tp hp l b nhng quyn c cng ch vi chi ph hp l.

Cu hi 8: Mi trng trong lnh l mt hng ho cng cng, li ch ca n khng th b mt ai chim ot lm ti sn ring. V vy, nghnh cng nghip t nhn tm kim li ch c nhn s lun lun l k th ca mi trng trong lnh. Hy bnh lun v tuyn b ny.

Gii p:

Nu mt hng ho cng cng c hai c im khng cnh tranh v khng loi tr (nh vy n l hng ho cng cng thun tu), khi th trng khng th cung cp hng ho ny vi mc cho php t hiu qu phn phi. iu ny gi rng nu mi trng trong lnh l mt hng ho cng cng thun tu, n s khng c cung ng y trn th trng m quyt nh cung do cc hng ti a ho li nhun thc hin. Thc cht, vic xem xt vn n theo gi rng c th c thiu cung tng th. Tuy nhin, mt mi trng trong lnh c m t ng n nh l mt hng ho cng cng thun tu l khng r rng. Cng nh vy khng th tng tng rng cc k hoch cn c thit k mc du chng khng hon ho m cc hng t nhn c n b cho vic cung cp hng ho cng cng mc ti u x hi. Nhng k hoch/chng trnh ny c th i hi, mt trong nhiu vic, thay i hnh thc quyn s hu ti sn. C th c li nhun t nhng hnh vi kinh doanh thn thin vi mi trng. Tuy nhin, gi nh rng hnh vi ca th trng khng b iu khin dng nh l th ch i vi mi trng trong lnh l hp l.

BI 4: TM LC CC KHI NIM C BN TRONG KINH T HC PHC LI

CH 1: Hiu qu th trng: Li ch (cu) v Chi ph (cung)

Ngun: Field & Olewiler (2002)

Cu 1: iu g xy ra i vi ng tng cu khi ngi tiu dng cho rng gi hng ha s tng (hoc gim) trong tng lai? Liu tnh hung ny c ph nhn l thuyt trnh by ch ny?

p n:

K vng v mc gi tng lai cao hn (thp hn) s dch chuyn ng cu qua bn phi (bn tri). Liu s suy on v gi c c ph nhn l thuyt cho rng th trng hot ng nhm ti a ha thng d s ph thuc vo suy on c ng hay khng. Gi s

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nim tin ca nhng ngi d on gi l ng, h s c gng li dng s tng gi ny, rng ngi ta s sn lng tr nhiu hn trong tng lai so v hm nay. Do vy, h s ng vai trn nhng ngi trung gian gia nhng ngi tiu dng c gi sn lng tr cao v nhng ngi c gi sn lng tr thp. Do nhng li ch t c t vic mua bn ny, s c s gia tng trong tha dng rng. Th hai l h s ng vai tr nhng phong v biu d bo nhng thay i trong tng lai. Mt s gia tng trong gi c s dn n doanh nghip tng sn lng. Hnh vi u c tch tr c th lm tng gi trong thi k u v t cc doanh nghip s tng sn lng ca h trong nhng nm sau. C s ca s gia tng v mc gi c th l s gia tng trong nhu cu, do vy vic d bo s gip nng cao xc sut cn bng th trng trong nm sau vi mc thng d t nhn cao hn. S d bo do vy cng c cng c. Mt khc, s d bo cng c th mt n nh v lm gim thng s x hi. Nim tin rng gi c s tng c th khng c mt c s ng n no v c th ch l mt hin tng t n gy ra. Nim tin sai lm rng gi c s tng c th dn n vic nhng nh u c mua hng ha v t lm tng gi... Mc gi tng c th dn n sn lng tng v do vy s c qu nhiu hng ha c sn xut trong nm tip theo, v nh vy gi s gim. Trong trng hp ny, nhng nh u c s l v ngi tiu dng cng vy t hin tng gi cao v cung thp. D cung trong nm tip theo c th dn n mc gi thp v gim thng d sn xut, dn n thit hi phc li rng.

Cu 2. Vic cn bng li ch v gi sn lng tr c th dn n kt lun rng vic lm sch khng kh m nhng ngi thu nhp thp ang sng trong s to ra t li ch hn so vi vic lm sch khng kh ca nhng ngi c thu nhp cao. Liu iu ny c ph nhn tng cn bng li ch v gi sn lng tr? Cc nh kinh t hc c th gii quyt vn ny nh th no?

p n:

Nhng suy xt v mt phn phi khng ph nhn khi nim gi sn lng tr nhng hm rng n phi c s dng cn thn, c bit l trong nhng trng hp lin quan n nhng ngi c mc thu nhp khc nhau. Trong nhiu trng hp y khng phi l vn quan trng. V d, so snh WTP vi mt th khc (nh cht lng mi trng) ca mt nhm c th, v xem xt s khc bit trong WTP gia cc nhm khng chnh lch ng k v thu nhp. Mt cch gii quyt nhng vn phn phi lin quan n cc nhm thu nhp khc nhau l gn trng s cho WTP bin. Trng s ny lm cho tha dng bin t mt -la i vi ngi ngho cao hn i vi ngi giu. Tng MB khi c tnh n kh nng chi tr khc nhau v gi sn lng tr.

Cu 3. Nhng nhn t no nh hng n hnh dng ca ng chi ph bin? Nhng nhn t ny c khc nhau ng k gia cc ngnh?

p n:

Hnh dng ca ng MC v c bn s ph thuc vo cng ngh c s dng. Cc yu t c th xem xt l cc yu t c nh, di hn so vi ngn hn, li tc tng, gim hay

12


khng i theo quy m. Mt s ngnh c th c nhiu yu t nh hng m rt kh tng trong ngn hn, dn n ng MC ngn hn tng rt nhanh. Kh nng thay th ca cc yu t sn xut, khong cch n th trng u vo, s thiu lao ng v cht lng lao ng gim st u nh hng n chi ph sn xut.

Cu 4. Hy gii thch cho mt ngi khng c chuyn mn v kinh t ti sao cc gi tr cn bin li quan trng trong phn tch kinh t. Bn s phn ng nh th no vi lp lun ca ngi rng h cha bao gi da vo cc gi tr cn bin trong vic ra quyt nh?

p n:

Cc nh kinh t hc gi nh rng cc c nhn v n v theo ui li ch c nhn, mc d iu ny khng hm ch ngha v k thun ty. H cng gi nh rng cc hot ng em li li ch v chi ph, v thng thng l c s nh i. Hy ngh hc vin th tng tng mt ngy khng c s nh i. V d, mc d vic thc dy em li nhiu li ch hn l vic ng thm mt pht, nhng nu h khng theo ui li ch c nhn th c th h s ng tip. H c th s khng ung c ph, mc d kinh nghim cho h bit rng nu khng c c ph h s b nhc u... Bn cng c th thy rng trong rt nhiu vic, h khng tun theo mt qu trnh ti u ha mt cch c thc. Tuy nhin, nu nhn li th h s nhn thy rng mc d khng ngh n, nhng h thng ng x theo cch rt gn vi vic cn bng li ch bin v chi ph bin.

CH 2: nh ngha v o lng nhng thay i v Phc li

Ngun: Field & Olewiler, 2002, Chng 3

Cu 1. Nhu cu ca Alvin i vi nc ng chai c biu din qua th QdA = 8 0.5P. Hm cu ca Betty l QdB = 6 P. Hy tnh tng gi sn lng tr v gi sn lng tr cn bin ca Alvin v Betty cho 4 chai nc v minh ha bng th.

p n:

ng cu c nhn th hin lng nc ti a m mi c nhn sn lng mua ti mt mc gi. Sp xp li phng trnh theo mc gi, ta c mt hm biu din mc gi ti a m mi c nhn sn lng tr (gi sn lng tr bin; MWTP) cho n v th Q. MWTPA =16-2 QdA v MWTPB =6 - QdB. Vi lng cu l 4 n v cho mi ngi, MWTP ca Alvin l $8, trong khi MWTP ca Betty l $2. Tng WTP ca Alvin l din tch nm di ng WTP bin ca anh ta t QdA = 0 n QdA =4, v tng t cho Betty. Tng WTPA = (8 x 4) x [(16-8) x 4]/2 = $48. Tng WTPB = (2 x 4) x [(6-2) x 4]/2 = $16.

13


16

8 6

2 0 0

4 8 4 6

Cu 2. Vi cc phng trnh nh trong Cu 1, hy tnh tng cu i vi nc ng chai, gi nh rng Alvin v Betty nhng ngi tiu dng duy nht. Xc nh ng tng cu nu c 5 ngi c ng cu nh Alvin v 5 ngi c ng cu nh Betty.

p n:

tnh tng cu ca Alvin v Betty, cng gp lng cu ti mi mc gi (cng theo chiu ngang). ng cu s gp khc mc gi $6, ti Alvin mua 5 v Betty mua 0 n v sn phm. H s ct trn trc gi l $16 v trn trc lng l 14 n v. Vi mc gi t 0 n 6, c hai ngi tiu dng s c nhu cu v nc ng chai, tnh tng lng cu s cho ta hm tng cu QdB & A = 14 3P/2. Vi mc gi cao hn $6, ch c Alvin l c nhu cu, t c hm cu QdB & A = 16 2P.

Vi 5 ngi tiu dng cho mi hm cu c nhn trn, hm tng cu cho 5 ngi ging Alvin v 5 ngi ging Betty tng ng l QdaggA = 40 2.5P v QdaggB =30 5P. ng tng cu ca 10 ngi l gp khc ti mc gi $6 v sn lng 25 n v. mc gi t 0 n 6, c th tm ra ng cu bng cch tnh tng lng cu ca 10 ngi Qdagg = 70 7.5P. Vi mc gi cao hn $6, ch c Alvin c nhu cu mua nc, vi tng cu l Qdagg = 40 2.5P. H s ct trn trc gi l $16 v trn trc lng l 55.

MWTP 16 ($/n v)

10

0 5 14 QdB & A

MWTP ($/n v)

MWTP ($/n v)

Qa Qa

14


Cu 3. Nu gi ca bng tennis l $4 cho mi container, nhng nh sn xut sau y c th tip tc sn xut hay khng? Ti sao? Mi ngi s sn xut bao nhiu ti mc gi ny?

p n:

Mi doanh nghip s thu c thng d t nhn dng nu li ch bin m n nhn c ( y l $4 trn mt n v) cao hn chi ph bin sn xut ra n v sn phm . Doanh nghip s c li nu MC P, v n s l. Chng ta c th tm ra sn lng ca mi doanh nghip bng cch t MC = P = 4 v tm n s. i vi doanh nghip A, kt qu l 3 + 0.3 Qs

=4, t Qs

=3.33 (1,000 n v). Tng t, doanh nghip B khng th cung ng n v sn lng no, trong khi doanh nghip C s cung cp 30 (1,000 n v).

Cu 4. ng cu ca mt c nhn i vi nc ung ng chai c biu din bi phng trnh: Q= 6- 0.5p + 0.0001I

Vi Q l lng cu ti mc gi p khi thu nhn ca c nhn l I. Gi s ban u thu nhp ca c nhn ny l $40,000.

a) Ti mc gi no th lng cu bng khng? Mc gi ny c gi l mc gi ti a (choke price) bi v n l mc gi trit tiu nhu cu.

b) Nu gi tt ca nc ng chai l $10, lng cu l bao nhiu? c) Ti mc gi $10, co gin ca cu theo gi l bao nhiu? d) Ti mc gi $10, thng d tiu dng l bao nhiu? e) Nu gi tng ln $12, thng d tiu dng s gim bao nhiu? f) Nu thu nhp l $60,000, thng d tiu dng b mt l bao nhiu nu mc gi tng

t $10 ln $12?

p n:

a) Q = 6 0.5p + 0.0001I Q = 6 0.5 p + 0.0001 (40,000) Q = 10 0.5p

Ti Q =0 P =20

b) Q = 10 0.5 (10) = 5

c) co gin ca cu theo gi l (q/p) (p/q). Vi ng cu tuyn tnh nh phng trnh trong bi ny, (q/p) bng dc ca ng cu, v trong bi tp ny l 0.5. Do co gin ca cu theo gi l (-0.5) (10/5) = -1. Lu rng vi

15


ng cu tuyn tnh, co gin ca cu theo gi l khng c nh, gi tr tuyt i ca n tng khi mc gi tng.

d) Thng d tiu dng l tam gic nm di ng cu (ngc) v trn mc gi cn bng. ng cao ca tam gic l mc gi ti a choke price tr gi tt (20-10 = 10) v y l lng cu (5). Din tch tam gic l (10) (5)/2=$25.

e) Mc gi tng ln $12 lm lng cu gim xung 4 chai. Thng d tiu dng mi l (20-12) (4)/2=$16. Phn gim trong thng d tiu dng l $25-$16=$9.

f) Khi thu nhp l $60,000, nh cu i vi nc ng chai l Q=6-0.5p+ (0.0001) (60,000) = 12 0.5p. Vi p = 10, q=7, v p=12, q=6, s thay i trong thng d tiu dng l (12-10) (6) + (2) (1)/2 = 13. S thay i trong thng d tiu dng tng ln theo thu nhp cho thy s ph thuc ca gi sn lng tr vo thu nhp.

Cu 5. Gi s mt nh my xay bt g c t b sng Mekong. Chi ph t nhn bin (MC) ca vic sn xut bt g ($/tn) c biu din qua phng trnh:

MC = 10 + 0.5 Y

Vi Y l tn bt g c sn xut. Bn cnh chi ph t nhn bin cn c mt chi ph ngoi tc. Mi tn bt g s to ra mt lung nhim cho con sng, to ra mt thit hi $10. y l mt chi ph ngoi tc do cng ng gnh chu ch khng phi do ngi gy nhim. Li ch bin (MB) i vi x hi ca mi tn bt, tnh theo $, l:

MB = 30 0.5 Y

a) Hy v th minh ha chi ph bin (MC), li ch bin (MB), chi ph ngoi tc bin (EMC), v hm chi ph x hi bin.

SMC = 20 +0.5Y

MC =10 +0.5 Y

MB= 30-0.5Y

EMC =10

Y*=10

b) Tm mc sn lng bt g ti a ha li nhun, gi s rng ngi bn c th t c doanh thu bin bng li ch bin ca x hi t bt g.

16


MC = 10 + 0.5 Y MR = 30 0.5 Y

MC = MR ti a ha li nhun:

10 + 0.5Y = 30 - 0.5Y- ta c Y* = 20.

c) Tm mc sn lng bt g ti a ha li ch x hi rng

Vi MEC =10 SMC = MC + MEC = 10 + 0.5Y + 10 = 20 + 0.5 Y v ti a ha li ch x hi rng i hi:

SMC = MB

Suy ra: 20 + 0.5 Y = 30 0.5 Y = > Y* = 10.

d) Chi ph ngoi tc bin phi l bao nhiu vic sn xut bt g khng cn ng mong mun i vi x hi?

MC + MEC = MB

10 + 0.5Y + MEC = 30 0.5Y- Y = 20 MEC.

Do , vi Y =0, MEC=20.

Cu 6. Gi s mt c nhn c hm tha dng:

U = E0.25 + Y 0.75

Vi E l ch s cht lng mi trng v Y l thu nhp. T tnh hung ban u vi E =1 v Y=100, tnh CS v ES tm ra s thay i do E ln 2 v E gim xung 0.5.

p n:

Vi s ci thin cht lng mi trng E, ta c:

U0 = 10.25 + 1000.75 = 32.6228

U1 = 20.25 + 1000.75 = 32.8120

CS l WTP cho s ci thin, do chng ta phi gii phng trnh:

32.6228 = 20.25 + Y0.75N

tm ra YN, nh sau:

17


32.6228 = 1.1892 + Y0.75N

Y0.75N = 31.4336

0.75ln(YN) = ln (31.4336) = 3.4479

ln (YN) = 4.5972

YN = 99.2032

Khi ,

CS = Y0- YN = 100 99.2032 = 0.7968

ES l WTA cho s ci thin b mt i, do ta phi gii:

32.8120 = 10.25 + Y0.75N

tm ra YN, kt qu l YN = 100.7928

Do ES = YN Y0 = 0.7928.

Vi s gim st cht lng mi trng E, ta c:

U0 = 10.25 + 1000.75 = 32.6228

U1 = 0.50.25 + 1000.75 = 32.4637

CS l WTA cho s thay i. Ta gii phng trnh:

32.6228 = 0.50.25 + Y0.75N

tm ra YN = 100.6815 kt qu l CS = YN Y0 = 100.6715 100 = 0.6715

ES l WTP khng xy ra s thay i, ta gii: 32.4637 = 10.25 + Y0.75N

tm ra YN = 99.3298, kt qu l ES = Y0 YN = 100 99.3298 = 0.6702

Cu 7. Ch c nhng tiu chun mi trng cao nht mi c th ti a ha phc li x hi. Hy bnh lun.

p n:

Pht biu ny ni ln rng cn phi huy ng mt cch khng gii hn cc ngun lc x l (hay phng chng) nhim hay suy thoi mi trng, bt k quy m ca li ch

18


m vic lm ny em li. Hiu qu kinh t i hi s cn bng gia li ch v chi ph bin. Tuy nhin, pht biu ny l ph hp vi vn hiu qu kinh t nu chi ph lm sch/ngn nga nhim lun bng khng, hay cc thit hi l ln v cng, hay ni mt cch tng qut hn, nu li ch bin di hn lun ln hn chi ph x l bin di hn cho n khi nhim c x l hon ton.

BI 5: KINH T NHIM MI TRNG

CH 1: Mc nhim ti u

Ngun: Field, Olewiler, and Forsdyke, 2002

Cu 1: Cho MNPB = 1000-10Q v MEC = 10Q. Gi s c sn xut mt n v sn phm th to ra mt n v nhim. Hy xc nh mc nhim ti u di dng thit hi hoc chi ph ngoi ng.

(1) Khi lng sn phm ti u l Q* tho mn iu kin cn bng cn bin. MNPB = MEC 1000 -10Q = 10Q Q* = 50 Mc nhim ti u tng ng vi mc sn lng Q* = 50 n v sn phm. mc sn lng ny tng thit hi l din tch pha di ng MEC t 0 n Q* hoc tam gic OEQ* bng (50 * 500)/2 = $ 1250.

CH 2: nh l Coase v quyn ti sn

Ngun: F, O, and F, 2002; (Perman, Ma, McGilvray, and Common, 2003)

Cu hi 1. Gi s ch th gy nhim c quyn ti sn v ch th b nh hng nhim phi chu ton b chi ph giao dch. Mc nhim s nh th no so snh vi trng hp chi ph giao dch bng khng?

50

MEC

MNPB

C,B

Q/W O 100

E

Q*

19


Gii p:

Khi ch th gy nhim c quyn ti sn, ch th b nh hng nhim s l ngi khi xng mc c. Nu ch th b nh hng nhim phi chu ton b chi ph giao dch, khi chi ph mc c ca ch th b nh hng nhim khng ch bao gm tin bi thng cho ch th gy nhim cho li nhun b mt i m c chi ph giao dch. iu ny hm rng ng chi ph cn bin MC trong mc c ca ch th b nh hng nhim l cao hn so vi trng hp chi ph giao dch bng khng. Trong khi MB ca ch th b nh hng nhim khng thay i. V vy mc nhim l c th cao hn so vi trng hp chi ph giao dch bng.

Cu hi 2: Trong hon cnh no mc c c th xy ra t c mc nhim hiu qu?

Gii p:

Mc c c th xy ra dn n mc nhim hiu qu khi: 1. Quyn ti sn c phn ch r rng 2. S ngi can d tng i t 3. Quan h nhn qu l r rng 4. Thit hi d o lng v chi ph giao dch kh thp.

Cu 3. Hy phn bit nh hng ngoi vi hng c nhn v hng cng cng. Tho lun kh nng mc c dn n phn phi ti nguyn hiu qu trong mi trng hp.

Gii p:

nh hng ngoi vi hng c nhn ch gy nh hng mt tp hp nht nh cc c nhn trong cng ng; ch th pht thi nhim c th kim sot c i tng b nh hng. nh hng ngoi v hng cng cng gy nh hng n tt c mi ngi trong cng ng; mi khi nh hng l tc ng n ngi ny th cng s tc ng n ngi khc.

Gii php mc c i vi nh hng ngoi vi hng cng cng thng t xut hin; v thm ch khi mc c xut hin, kt qu thng t khi hiu qu. Nguyn nhn mt phn l do s lng ngi b tc ng bi nh hng ngoi vi thng kh ln. Xc nh v lin lc gia cc i tng b nh hng v t chc mc c thng c chi ph cao v kh khn. Nguyn nhn khc c th ny sinh t vn n theo; cc c nhn thng khng tit l ng gi ch quan thc cht ca h v nh hng ngoi vi, hoc c gn ln trnh ph tn nu tham gia trc tip vo qu trinh mc c.

CH 3: Tiu chun mi trng

Ngun: Field, Olewiler, v Forsdyke, 2002; Perman, Ma McGilvray, v Common, 2003

20


Cu hi 1: Hy lit k v gii thch ba vn /hn ch ca tiu chun cng ngh, s dng th h tr tr li.

Gii p:

Tiu chun cng ngh c tc dng hn ch trong vic khuyn khch pht trin v p dng cng ngh x l c chi ph thp hn tiu chun. Trn th, MAC ca cng ngh quy nh l cao hn ca cc cng ngh sn c khc hoc cha sng ch. Tiu chun cng ngh gim thp kh nng linh hot ca doanh nghip gim chi ph x l theo cch thc tit kim nht c th c. V d, phng php qun l tit kim chi ph hn c th c khm ph thng qua hc t thc t; nhn vin chnh ph khng th d bo nhng k thut nh vy. iu ny dn n vn ph thuc tuyn; khng phi chnh ph m nh my c kh nng tt hn trong tm kim trong khng gian cng ngh pht hin c qu o cng ngh x l hiu qu nht theo thi gian.

Nh my c th khng p dng k thut c chi ph thp v s b kt ti khng tun th. Nhn vin chnh ph c th hon ton khng linh hot, v c ng c hn ch linh hot vi nhng nh my nm bt nhng phng php x l tt hn. Mt ch th v nn tho lun l nh hng ca tiu chun cng ngh i vi cng nghip kim sot nhim. Nu bit rng chnh ph s p dng mt cng ngh, c th c gii thng ln cho vic c kh nng nm bt kp tiu chun tip theo. Tr cp pht trin cng ngh sch c th cho php pht trin quan h hp tc gia cc ngnh, i lp vi quan h i nghch thng thy gia chnh ph v doanh nghip trong qun l mi trng.

Chnh ph thiu thng tin v phng tin x l r nht (so vi doanh nghip) v thiu ng c pht trin v thc hin cng ngh x l cht thi tit kim chi ph nht. Hn th na, cng ngh x l r nht l c th cho tng doanh nghip; theo ngha ny tiu chun cng ngh l ng b. Chi ph cng ch c th cao, bi v cn phi gim st c tun th ban u v tun th tip tc. Thit b x l cn c kim tra xem c hot ng v s dng theo ng quy nh hay khng. Bi v quy nh do cp quc gia t ra nhng li c cng ch/thc thi cc a phng, khng c g m bo rng cc nhn vin a phng c ngn sch hoc chuyn mn cng ch ng n cc tiu chun. Bn cht ng b ca cc tiu chun c n v hiu qu gia cc nhm. V d, khu vc nng thn do hm lng cht gy nhim mi trng xung quanh thp, doanh nghip c th buc phi s dng cng ngh m chi ph x l cn bin vt qu thit hi cn bin gim c.

Cu 2: Loi tiu chun no c th s dng cho ngun nhim khng c im ngun (non-point) (v d: ho cht nng nghip t sn xut nng nghip) v nhim do mi ch th gy nn khng th o lng c? Gii thch, ti sao

Gii p:

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