2.4.3.1 nemaresiphi Natural

Nemaresiphi Natural ukusizakala izenzakalo ezingahleliwe in the world. Umcimbi okungahleliwe + ngaso sonke isikhathi-on ohlelweni idatha = experiment yemvelo

Isihluthulelo randomized kocwaningo olwenza kuqhathanisa fair iyona eqenjini. Nokho, kwenzeka ngezikhathi ezithile okuthile emhlabeni ngokuyisisekelo esabela abantu ngezikhathi noma ecishe ngezikhathi zokwelapha ezahlukene. Omunye izibonelo ezicacile isu usebenzisa nemaresiphi zemvelo livela locwaningo Angrist (1990) ukuthi ulinganisa umphumela kwezinsizakalo wezempi on umholo.

Phakathi nempi yaseVietnam, United States anda ubukhulu amabutho akhe ahlomile amasha ngokusebenzisa okusalungiswa. Ukuze banqume ukuthi yikuphi izakhamuzi yayiyobizwa ngokuthi enkonzweni, uhulumeni wase-United States labetibambile ilotho. Njalo Usuku lokuzalwa eyayifanekiselwa on ephepheni, futhi lezi amaphepha zafakwa ingilazi nembiza enkulu. Njengoba kuboniswe ePhuzwini 2.5, lezi zithombo iphepha zithathelwe embizeni eyodwa ngesikhathi ukuthola ncamashí ukuhlelwa izinsizwa babeyiswa ukukhonza (ntombi kwakufanele isidingo sokulalela okusalungiswa). Ngokusekelwe imiphumela, amadoda azelwe ngoSepthemba 14 ayebizwa ngokuthi okokuqala, amadoda azelwe ngo-April 24 Kube sekubizwa wesibili, nokunye. Ekugcineni, kule lottery, amadoda azelwe ngezinsuku ezahlukene 195 abizelwe inkonzo ngesikhathi amadoda azelwe ngezinsuku 171 babengabuthelwa.

Figure 2.5: lesiShaya Alexander Pirnie (R-NY) sifinyelela capsule yokuqala okusalungiswa okukhetha Service ngoDisemba 1, 1969 uJoshuwa Angrist (1990) kuhlangene lottery okusalungiswa ngedatha Amaholo kusukela Administration Social Security ukulinganisa umphumela senkonzo yezempi on Amaholo. Lesi isibonelo yocwaningo usebenzisa experiment yemvelo. Source: Wikimedia Commons

Nakuba kungase kungabi ngokushesha, lottery okusalungiswa has a ukufana esibucayi kuya randomized ukuhlola: kuzo zombili izimo ababambiqhaza lwafaka ukuthola ukwelashwa. Endabeni lottery uhlaka, uma sinesithakazelo kwesikwenzayo ukufunda ngemiphumela okusalungiswa-yokufaneleka kanye ukungenela inkonzo yezempi ngenxa okwalandela wezabasebenzi Amaholo, singakwazi qhathanisa imiphumela kwabantu abanjabulo yabo birthdates ayengaphansi kwama the cutoff lottery (isib, September 14, April 24, njll) ne imiphumela kwabantu abanjabulo yabo zokuzalwa ngamashumi emva cutoff (isib, February 20, December 2, njll).

Njengoba sazi ukuthi lokhu kwelashwa kumanje uyabhalwa iye lwafaka, singakwazi ke ukukala umphumela walesi ukwelashwa nganoma yisiphi isiphetho iye kulinganiswa. Ngokwesibonelo, Angrist (1990) kuhlangene ulwazi mayelana owayebizwa ngezikhathi akhethiwe okusalungiswa nge idatha Amaholo ukuthi kwaba eqoqwe uMthetho wokuPhathwa Social Security ukuphetha ngokuthi imali Veterans white ayemancane angaba ngu-15% kunanoma ngemali engaqhathaniswa non-Veterans . Abanye abacwaningi baklame wasebenzisa iqhinga efanayo kanye. Ngokwesibonelo, Conley and Heerwig (2011) kuhlangene ulwazi mayelana owayebizwa ngezikhathi akhethiwe okusalungiswa nge idatha nendlu eqoqwe kusukela 2000 Census and 2005 American Community Survey futhi bathola ukuthi isikhathi eside kangaka ngemva okusalungiswa, kuncane nomphumela owaqhubeka isikhathi eside ukungenela inkonzo yezempi ngenxa ezihlukahlukene kwemiphumela ezifana nezezindlu ngokuphathelene namalungelo okusebenzisa umhlaba (ngizoke Ukuqhathanisa liqashe) nokuqina kuyivelakancane zokuhlala (Uzomangala ukuthola ukuthi siye wathuthela owedlule iminyaka emihlanu).

Njengoba lesi sibonelo sibonisa, ngezinye izikhathi ezenhlalo, ezombusazwe, noma iyaziveza kwenziwa ucwaningo noma eduze-ukuhlolwa kungenziwa leveraged abacwaningi. Ngokuvamile kwenziwa ucwaningo yemvelo ngendlela engcono ukulinganisa ubudlelwano imbangela nemphumela kuzilungiselelo lapho akusiyo sokuziphatha noma ezingokoqobo ukugijima randomized kocwaningo. Ziyakwazi isu ebalulekile yokuthola iziqhathaniso fair in idatha non-zokuhlola. Lelisu ucwaningo kungenziwa ngokufingqiwe yilo ezothando:

\ [\ umbhalo {okungahleliwe (noma sengathi okungahleliwe) mcimbi} + \ umbhalo {njalo-ekusakazeni idatha} = \ umbhalo {experiment zemvelo} \ qquad (2.1) \]

Nokho, ukuhlaziywa ucwaningo yemvelo ingase iqonde olukhohlisayo. Ngokwesibonelo, uma kwenzeka kuba yeVietnam uhlaka, akuwona wonke umuntu kwaba okusalungiswa-abafanelekile bagcina ukukhonza (kwakukhona ezihlukahlukene ekukhokheni). Futhi, ngesikhathi esifanayo, abanye abantu abangabulawanga ekubhaleni-abafanelekile wazicelela ukujoyina. Kwaba sengathi ecaleni emitholampilo umuthi omusha, abanye abantu eqenjini ukwelashwa akazange imithi yabo futhi abanye abantu eqenjini control ngandlela-thile wathola umuthi. Le nkinga, okuthiwa ukungahambisani amabili emaceleni, kanye nezinye izinkinga eziningi zichazwe ngokuningiliziwe ezinye ukufundwa Kunconywa ekupheleni kwalesi sahluko.

Indlela sibambe zemvelo isabelo okungahleliwe obulandela age digital, kodwa nokudlanga idatha big kwenza lelisu lula kakhulu ukusebenzisa. Uma uqaphele ezinye ukwelashwa okwabelwe nemiyalezo, big imithombo idatha anganikeza idatha umphumela oyidingayo ukuze uqhathanise imiphumela abantu ekwelapheni kanye nokulawula izimo. Ngokwesibonelo, ekutadisheni kwakhe yemiphumela okusalungiswa futhi empini, Angrist yasebenzisa Amaholo amarekhodi Administration Social Security; ngaphandle le datha umphumela, isifundo sakhe kwakungeke kube yimpumelelo. Kulokhu, Administration Social Security yiyona njalo-on big umthombo idatha. Njengoba more and more ngokuzenzakalelayo eqoqwe data imithombo akhona, siyoba nokuningi idatha nomphumela elingase ukukala Imiphumela yalolo shintsho adalwe ukushintshashintsha exogenous.

Ukuze sifanekise lelisu in the age digital, ake sicabangele Mas futhi Moretti sika (2009) ucwaningo nenhle umphumela ontanga on umkhiqizo. Nakuba phezu kungase zibukeke ezahlukene ukwedlula isifundo Angrist sika ngemiphumela yeVietnam Draft, isakhiwo bobabili ukulandela isibonelo EQ. 2.1.

Mas futhi Moretti kulinganiswa kanjani ontanga ezithinta umkhiqizo abasebenzi. Ngakolunye uhlangothi, abanesimo untanga kanzima esingase siholele abasebenzi ukwandisa umkhiqizo wabo ngenxa yokucindezela kontanga. Noma, Ngakolunye uhlangothi, ontanga kanzima esingase siholele nezinye izisebenzi ukuba owenqenayo off ngisho nangokwengeziwe. Indlela ecacile ukutadisha peer imiphumela lokukhiqiza ubuyoba randomized ukuhlola lapho abasebenzi lwafaka ukuba amashifu nabasebenzi abasemazingeni ahlukahlukene lokukhiqiza bese kwaphumela nemikhicito kukalwa kuwo wonke umuntu. Abacwaningi Nokho, musa ukulawula esimisweni abasebenzi kunoma yiliphi ibhizinisi real, futhi kanjalo Mas futhi Moretti kwadingeka ukuba bathembele sokuhlolwa yemvelo okwenzeka esitolo.

Just like EQ. 2.1, isifundo sabo kwadingeka izingxenye ezimbili. Okokuqala, babesebenzisa izingodo kusukela ohlelweni esuphamakethe okukhokhwa ukuba abe eqondile, ngabanye, futhi njalo-on nesilinganiso lokukhiqiza: nenani lezinto bangahlola ngomzuzwana. Futhi, okwesibili, ngoba indlela ukuhlela kwakwenziwa ngalesi esitolo banayo eduze ukubunjwa okungahleliwe ontanga. Ngamanye amazwi, yize ukuhlela izisebenzi ayinqunywa lottery, kwaba ngokuyisisekelo okungahleliwe. Ngo practice, ukuqiniseka esinakho ucwaningo zemvelo njalo buxhomeke the mbono yale "njengoba uma" funa okungahleliwe. Sibambe lokhu ukushintshashintsha okungahleliwe, Mas futhi Moretti yathola ukuthi ukusebenza ephakeme nontanga lokukhiqiza kwandisa umkhiqizo. Ngaphezu kwalokho, Mas futhi Moretti esetshenziswa ubukhulu kanye ukujula kwedathasethi kwabo ukudlulela ngale ukulinganisa imbangela nemphumela ukuyihlola izimpikiswano ezimbili ezibaluleke kakhudlwana futhi ezicashile: heterogeneity of ngalokhu (okuyiwona izinhlobo abasebenzi umphumela ezinkudlwana) kanye mshini ngemuva umphumela (kungani kokuba okusezingeni lokukhiqiza ontanga kuholele umkhiqizo ephakeme). Sizobuye kulezi ezimbili ezibalulekile nezindaba-heterogeneity imiphumela ukwelashwa kanye netindlela-eSahlukweni 5 lapho sixoxa ucwaningo ngokuningiliziwe ngokwengeziwe.

Generalizing izifundo on the umphumela Vietnam Draft on Amaholo kanye nesifundo emphumeleni ontanga on lokukhiqiza, Ithebula 2.3 Kubhala sifinyeto ngekusitwa nezinye izifundo ukuthi unaso lesi esiqondile sakhiwo lesifanako: usebenzisa i njalo-on umthombo wemininingwane ukukala umthelela abathile umcimbi . Njengoba Ithebula 2.3 kwenza kucace, ucwaningo zemvelo akuyo yonke indawo uma nje wazi kanjani ukuzibheka.

Ngo practice, abacwaningi babuye basebenzise amasu ezimbili ezahlukene sokuthola nemaresiphi zemvelo, zombili ezimane tingaba nemphumela lomuhle kakhulu. Abanye abacwaningi kuqale njalo-on idatha umthombo futhi afune izinto ezithuka zenzeka emhlabeni; abanye uqale nge izenzakalo ezingahleliwe in the world futhi afune imithombo idatha ukuthi liyobamba umthelela wabo. Ekugcineni, phawula ukuthi amandla ucwaningo yemvelo asiveli yinkimbinkimbi analysis kwezibalo, kodwa isuka ekunakekelweni in ethola ukuqhathanisa ukujabulisa owadalwa a engozini ngibusiseke yomlando.