2.4.3.2 mufananize

Zofanana kulenga kufananitsa chilungamo ndi kumathandiza kuti zinthu zikhale kutali milandu.

kufananitsa Fair angabwere kapena zatsopano osapanganika kulamulidwa kapena zatsopano zachilengedwe. Koma, pali zinthu zambiri kumene mukhoza kuthamanga kuyesa abwino ndi chikhalidwe alibe anapereka kuyesera zachilengedwe. Zoikamo izi, njira yabwino kulenga fanizo chilungamo ndi zofanana. Mu yofananira, kafukufuku amayang'ana kupyola deta si experimental kulenga awiriawiri anthu ofanana koma mmodzi alandira chithandizo ndi wina alibe. M'kati yofananira, ofufuza kwenikweni komanso kumathandiza kuti zinthu zikhale; kuti, kutaya nthawi imene palibe poyerekeza zoonekeratu. Motero, njira imeneyi angafune molondola wotchedwa yofananira ndi kudulira, koma ine kutsatira liwu mwambo: yofananira.

A chitsanzo chabwino cha mphamvu ya zofanana njira ndi yaikulu magwero sanali experimental deta anachokera kafukufuku pa ogula khalidwe ndi Liran Einav ndi anzake (2015) . Einav ndi anzake anali ndi chidwi amagulitsa nsombazo zikuchitika pa eBay, ndi kufotokoza ntchito yawo, ine kuganizira makamaka mbali imodzi: zotsatira za ogulitsira malonda kuyambira mtengo pa zakambidwa yobetcherana, monga mtengo malonda kapena Mwina chogulitsa.

Njira yosavuta wozindikira kuyankha funso za zotsatira za mtengo poyambira pa malonda mtengo adzakhala ndi chabe kuwerengera mtengo omaliza amagulitsa nsombazo ndi mitengo yosiyanasiyana poyambira. njira imeneyi zingakhale zabwino ngati inu mukungofuna kulosera za malonda mtengo wa katunduyo anapatsidwa kuti anali kuvala eBay ndi kuperekedwa mtengo poyambira. Koma, ngati funso lanu ndi chiyani zotsatira za kuyambira mtengo pa zakambidwa msika njira chithe chifukwa sayendera kufananitsa chilungamo; amagulitsa nsombazo ndi mitengo m'munsi poyambira akhoza kukhala osiyana kwambiri ndi amagulitsa nsombazo ndi wokwera poyambira (mwachitsanzo, iwo akhoza kukhala a mitundu yosiyanasiyana ya katundu kapena monga osiyanasiyana ogulitsa).

Ngati ndinu nkhawa moyerekeza chilungamo, inu mukhoza mwadya njira wosachangamuka ndi kuganizira kuthamanga munda kuyesera kumene mukufuna kugulitsa enieni item-kunena, gofu club-chili ndi amodzi a yobetcherana magawo-kunena, kutumiza free, yobetcherana lotseguka kwa masabata awiri, etc. koma ndi mosintha anapereka kuyambira mitengo. Amayerekezera chifukwa zakambidwa msika, kuyesera munda ndiwapatsa muyeso momveka bwino zotsatira za kuyambira mtengo pa malonda mtengo. Koma kudziwa zimenezi zikanapangitsa ntchito kwa mankhwala wina ndi ya magawo yobetcherana. Zotsatira angakhale osiyana, mwachitsanzo, kwa mitundu yosiyanasiyana ya mankhwala. Popanda chiphunzitso wamphamvu, n'zovuta extrapolate ku kuyesera single uthunthu wonse wa zatsopano zotheka kuti akanatha kuthamanga. Komanso zatsopano kumunda mtengo mokwanira kuti akhale infeasible kuthamanga mokwanira iwo kuphimba lonse chizindikiro danga la mankhwala ndi mitundu yobetcherana.

Mosiyana ndi njira wosachangamuka ndi njira experimental, Einav ndi anzake amachitanso lachitatu: yofananira. Mochenjera waukulu njira zawo ndi kupeza zinthu zofanana zatsopano munda zimene zinachitika pa eBay. Mwachitsanzo, Chithunzi 2.6 limasonyeza ena mindandanda 31 kwa chimodzimodzi gofu club wa Taylormade Burner 09 Oyendetsa-kugulitsidwa ndi chimodzimodzi seller- "budgetgolfer". Komabe, mindandanda awa ndi makhalidwe osiyana pang'ono. Khumi a iwo kupereka dalaivala mtengo lokhazikika la $ 124,99 pamene winayo 20 amagulitsa nsombazo ndi madeti osiyanasiyana mapeto. Komanso, mindandanda ali malipiro osiyana kutumiza, mwina $ 7,99 kapena $ 9,99. M'mawu ena, zimakhala ngati "budgetgolfer" ikutha zatsopano kwa akatswiri a.

Mindandanda wa Taylormade Burner 09 Oyendetsa kugulitsidwa ndi "budgetgolfer" ndi chitsanzo chimodzi cha akonzedwa chikufanana wa mindandanda, kumene yeniyeni item womwewo kugulitsidwa ndi yeniyeni wogulitsa yomweyo koma nthawi iliyonse ndi makhalidwe osiyana pang'ono. Mwa mitengo ikuluikulu ya eBay pali kwenikweni masauzande kukukhala chikufanana zokhudza mamiliyoni mindandanda. Choncho, m'malo kuyerekezera mtengo omaliza amagulitsa nsombazo zonse mwa anapatsidwa mtengo poyambira, Einav ndi anzake kudziyerekezera mkati waika chikufanana. Kuti kuphatikiza zotsatira za kufanana mwa mazana awa a zikwi kukukhala chikufanana, Einav ndi anzake kukonzanso kufotokoza mtengo poyambira ndi mtengo womaliza mwa mawu a mtengo buku lililonse item (mwachitsanzo, pa avareji zogulitsa mtengo). Mwachitsanzo, ngati Taylormade Burner 09 Oyendetsa ali wofunika Buku la $ 100 (yochokera malonda ake), ndiye mtengo poyambira wa $ 10 adzafotokozedwere monga 0,1 ndi mtengo chomaliza cha $ 120 adzafotokozedwere monga 1.2.

Chithunzi 2.6: Chitsanzo cha akonzedwa chikufanana. Izi ndi chimodzimodzi gofu club (a Taylormade Burner 09 Oyendetsa) kugulitsidwa ndi chimodzimodzi munthu ( "budgetgolfer"), koma ena a malonda amenewa anachita zinthu zosiyana (mwachitsanzo, osiyana poyambira mtengo). Chithunzi anatengedwa kuchokera Einav et al. (2015) .

Kumbukirani kuti Einav ndi anzake anali ndi chidwi ndi zotsatira za mtengo chiyambi pa zakambidwa yobetcherana. Choyamba, ntchito liniya mgwirizano akuganiza kuti apamwamba mitengo poyambira kuchepa Mwina chogulitsa, ndipo apamwamba mitengo poyambira kuonjezera chomaliza zogulitsa mtengo, makonzedwe pa chogulitsa zikuchitika. Paokha, izi ziwerengero-zimene pakuchitika pa zinthu zonse ndi chibale liniya pakati pa mtengo poyambira ndipo komaliza tikaona si onse chidwi. Koma, Einav ndi anzake ntchito kukula waukulu deta awo chaka zosiyanasiyana anapezazo zobisika kwambiri. Choyamba, Einav ndi anzake anapanga ziwerengero izi payokha zinthu za mitengo yosiyanasiyana ndi opanda ntchito liniya mgwirizano. Anapeza kuti ngakhale ubale mtengo kuyamba Mwina chogulitsa ndi liniya, ubale mtengo poyambira ndi mtengo malonda ndi bwino sanali liniya (Chithunzi 2.7). Makamaka, chifukwa kuyambira mitengo pakati 0,05 ndi 0,85, mtengo poyambira ali zimakhudza kwenikweni zogulitsa mtengo, ndi kupeza amene anamaliza anasowa kusanthula amene amaganiza ubale liniya.

Kuzilingalira 2,7: Ubale pakati yobetcherana chiyambi mtengo ndi Mwina chogulitsa (anasiya gulu) ndi zogulitsa mtengo (gulu kumanja). Pali ziri pa ubwenzi liniya pakati pa mtengo kuyamba Mwina kugulitsa, koma pali chiyanjano sanali liniya pakati pa mtengo chiyambi ndi mtengo kugulitsa; pakuti kuyambira mitengo pakati 0,05 ndi 0,85, mtengo poyambira ali zimakhudza kwenikweni zogulitsa mtengo. Nthawi zonse, ubale ndi kwenikweni osadalira pa mtengo item. Chintchito amenewa kubereka mkuyu 4a ndi 4b Einav et al. (2015) .

Chachiwiri, m'malo pafupifupi zinthu zonse, Einav ndi anzake komanso ntchito pamlingo waukulu deta awo amanena mmene kuyambira mtengo siyana 23 yosiyanasiyana ya zinthu (mwachitsanzo, katundu Pet, zamagetsi, masewero memorabilia) (Chithunzi 2.8). Ziwerengero amenewa akusonyeza kuti more chosiyana zinthu monga mtengo memorabilia-chiyambi kumakhudza zing'onozing'ono pa Mwina chogulitsa ndi zotsatira zikuluzikulu pa mtengo chomaliza zogulitsa. Komanso zambiri commodified zinthu monga ma DVD ndi kanema-mtengo chiyambi ali pafupifupi ndekuti mtengo chomaliza. M'mawu ena, avareji kuti Chili zotsatira siyana 23 yosiyanasiyana ya zinthu amabisa zinthu zina zofunika zokhudza kusiyana zinthu zimenezi.

Kuzilingalira 2.8: Results anasonyeza ziwerengero za aliyense m'gulu payekha; dontho olimba akuganiza kuti magulu onse pooled pamodzi (Einav et al. 2015, Table 11) . Ziwerengero amenewa akusonyeza kuti more chosiyana zinthu monga memorabilia-mtengo chiyambi kumakhudza zing'onozing'ono pa Mwina chogulitsa (x-olamulira) ndi zotsatira zikuluzikulu pa chomaliza zogulitsa mtengo (Y-olamulira).

Ngakhale ngati simuli chidwi amagulitsa nsombazo pa eBay, inu muyenera amasirira mmene chithunzi 2,7 ndi chithunzi 2.8 kupereka kumvetsa olemera okha a eBay kuposa ziwerengero yosavuta liniya mgwirizano kuti amaganiza mabwenzi liniya ndi kuphatikiza magulu osiyanasiyana zinthu. Izi akuti alipo zobisika kwambiri zikusonyeza mphamvu ya zofanana mu deta chachikulu; Ziwerengero izi sizikanatheka kukanakhala opanda nambala yaikulu kwambiri zatsopano munda, zomwe zinali prohibitively mtengo.

Kumene, tiyenera kupatula kudalira zotsatira za kafukufuku iliyonse makamaka yofananira kuposa ife masiku zotsatira za kafukufuku ofanana. Pamene akuona Kafukufuku aliyense yofananira, pali zinthu ziwiri zofunika. Choyamba, tiyenera kukumbukira kuti ife tikhoza kuonetsetsa kufananitsa chilungamo pa zinthu zimene ankagwiritsa ntchito yofananira. Zotsatira yaikulu, Einav ndi anzake Kodi yeniyeni zofanana pa makhalidwe anayi: wogulitsa ID number, item m'gulu, mutu item, ndi subtitle. Ngati zinthu zinali zosiyana m'njira kuti sanali ntchito yofananira, yemwe akanakhoza kulenga poyerekeza mokondera. Mwachitsanzo, ngati "budgetgolfer" adatchithisira mitengo Taylormade Burner 09 Oyendetsa m'nyengo yozizira (pamene ndodo za gofu sakhala wotchuka), ndiye tikhoza kuona kuti m'munsi mitengo poyambira kutsogolera kuchepetsa mitengo yomaliza, pamene ndiye kuti bokosilo wa nyengo akusinthasintha ankafuna. Ambiri, njira yabwino yothetsera vuto limeneli akuoneka kuti ankayesa zosiyanasiyana yofananira. Mwachitsanzo, Einav ndi anzake kubwereza zothandiza pamene likulowa chikufanana ndi monga zinthu zogulitsa chaka chimodzi, pasanathe mwezi umodzi, ndipo contemporaneously. Kupanga nthawi window molimbira amachepetsa chiwerengero kukukhala chikufanana, koma kumachepetsa nkhawa kusintha nyengo. Mwamwayi, amaona kuti zotsatila m'pang'ono ndi kusintha mu muyezo zofanana. Mu mabuku yofananira, mtundu zokhudza nthawi anasonyeza mwa mawu a observables ndi unobservables, koma lingaliro ofunika kwenikweni kuti ofufuza yekha kupanga kufananitsa chilungamo pa mbali ntchito yofananira.

The yaikulu nkhawa lachiwiri pamene kutanthauzira zotsatira zogwirizana ndi zimene iwo okha kutsatira kafukufuku chikufanana; iwo ntchito kwa milandu kuti sakanatha chikufanana. Mwachitsanzo, NADZIWA kafukufuku wawo kuti zinthu anali kangapo Einav ndi anzake ndi moganizira ogulitsa akatswiri ndi theka-akatswiri. Choncho, pamene kutanthauzira kufananitsa zimenezi tiyenera kukumbukira kuti iwo wokha ntchito kuti kagawo lino la eBay.

Yofananira ndi njira yamphamvu kupeza kufananitsa wokoma datasets lalikulu. Asayansi ambiri chikhalidwe, yofananira akuona ngati wachiwiri bwino zatsopano, koma kuti chikhulupiriro chakuti ayenera kuzilemba, pang'ono. Yofananira mu deta chachikulu zingakhale bwino kuposa ochepa zatsopano kumunda: 1) heterogeneity mu zotsatira n'kofunika ndi 2) pali observables zabwino yofananira. Table 2.4 amapereka zitsanzo zina za mmene zofanana angagwiritsidwe ntchito ndi magwero aakulu deta.

Pomaliza, njira wozindikira kuyerekeza zotsatira causal pazimene sanali experimental ali oopsa. Komabe, njira yopanga ziwerengero causal atagona pamodzi ndi popitilira kuchokera kwambiri anafooka, ndipo ofufuza mukhoza kupeza kufananitsa chilungamo mwa deta si experimental. Kukula kwa ka nthawi zonse pa lalikulu deta kumawonjezera luso lathu mogwira ntchito njira ziwiri alipo: zatsopano zachilengedwe ndi yofananira.