2.4.3.2 Matching

Txuam tsim kev ncaj ncees kev sib piv los ntawm pruning deb tus neeg mob.

Fair sib piv yuav los ntawm tog twg los xaiv tswj thwmsim los yog tej yam ntuj tso thwmsim. Tab sis, muaj ntau ntau zaus nyob qhov twg koj yuav tsis khiav zoo tagnrho xyaum ua tej yam thiab xwm tau tsis muab ib tug natural xyaum ua tej yam. Nyob rau hauv cov chaw, qhov zoo tshaj plaws txoj kev uas yuav tsim ib tug ncaj ncees sib piv txuam. Nyob rau hauv txuam, tus kws tshawb fawb zoo los ntawm uas tsis yog-cov ntaub ntawv los mus tsim officers ntawm cov neeg uas zoo sib xws tsuas yog hais tias muaj ib tug tau txais cov kev kho mob thiab ib tug muaj tsis tau. Nyob rau hauv tus txheej txheem ntawm txoj kev, soj ntsuam ntawm yog ua tau kuj pruning; uas yog, muab pov tseg tus neeg mob qhov twg muaj tsis muaj cuab kev sib piv. Yog li, qhov no txoj kev yuav tau ntau kom meej hu ua piv-thiab-pruning, tab sis kuv mam li lo nrog cov tus tsoos sij hawm: txuam.

Ib tug zoo nkauj piv txwv ntawm lub hwj chim ntawm txoj kev tswv yim nrog loj heev uas tsis yog-cov ntaub ntawv qhov chaw los ntawm cov kev tshawb fawb nyob rau hauv cov neeg coj tus cwj pwm los ntawm Liran Einav thiab lug txhawb cov miv (2015) . Einav thiab lug txhawb cov miv twb xav nyob rau hauv auctions noj qhov chaw nyob rau eBay, thiab nyob rau hauv piav txog lawv kev ua hauj lwm, kuv mam li ua kom pom tseeb rau ntawm ib tug nam: cov nyhuv ntawm auction pib nqi rau auction tau, xws li cov nqi muag los yog qhov tshwm sim rau ib tug muag.

Qhov tseem naïve txoj kev uas yuav teb cov lus nug txog cov nyhuv ntawm starting nqi ntawm kev muag khoom nqi yuav cias xam qhov kawg nqi rau auctions nrog txawv starting nqi. Qhov no mus kom ze yuav zoo yog hais tias koj tsuas xav mus twv seb tus nqi muag ntawm ib tug muab yam khoom uas tau raug muab tso rau hauv eBay nrog ib tug muab starting nqi. Tab sis, yog tias koj lo lus nug yog dab tsi yog qhov ua rau ntawm pib nqi rau kev ua lag luam tshwm sim no mus kom ze yuav tsis ua hauj lwm vim hais tias nws tsis yog raws li nyob rau hauv kev ncaj ncees kev sib piv; lub auctions nrog qis starting nqi tej zaum yuav txawv heev los ntawm auctions nrog ntau dua starting nqi (xws li, lawv tej zaum yuav rau ntau hom kev ntawm cov khoom los yog muaj xws li sib txawv ntawm cov sellers).

Yog hais tias koj twb yeej muaj kev txhawj xeeb txog kev ua ncaj ncees sib piv, tej zaum koj yuav hla lub naive mus kom ze thiab xav txog khiav ib daim teb xyaum ua tej yam uas koj yuav muag ib lub yam khoom-hais, ib tug golf qws-nrog ib tug taag set ntawm auction tsis-hais, free shipping, auction qhib rau ob lub lis piam, etc.-tab sis nrog across teem pib nqi. By muab piv rau cov uas ua lag luam tau, daim teb no xyaum ua tej yam yuav muaj ib tug heev ntshiab ntsuas ntawm cov nyhuv ntawm pib nqi rau nqi muag. Tab sis, qhov no ntsuas yuav tsuas siv tau rau ib qho kev khoom thiab teem ntawm auction tsis. Cov kev tshwm sim tej zaum yuav sib txawv, piv txwv li, rau ntau hom kev ntawm cov khoom. Tsis muaj muaj zog kev tshawb xav, nws yog ib qhov nyuaj rau extrapolate los ntawm no ib sim rau tag nrho cov ntau yam ntawm tau thwmsim uas yuav muaj tau khiav. Ntxiv mus, teb thwmsim yog sufficiently kim hais tias nws yuav infeasible khiav txaus lawv kom npog tag nrho parameter qhov chaw ntawm cov khoom thiab auction hom.

Nyob rau hauv sib piv rau lub naive mus kom ze thiab cov kev sim mus kom ze, Einav thiab lug txhawb cov miv coj ib tug thib peb mus kom ze: txuam. Lub ntsiab ua kom yuam kev ntawm lawv lub tswv yim yog nrhiav tau tej yam uas zoo xws li cov teb thwmsim uas twb tshwm sim nyob rau hauv eBay. Piv txwv li, Daim duab 2.6 qhia tau hais tias ib co ntawm cov 31 faib rau raws nraim tib yam golf qws-ib Taylormade Burner 09 tsav-raug muag los ntawm cov raws nraim tib yam seller- "budgetgolfer". Txawm li cas los, cov faib muaj txawv me ntsis yam ntxwv. Kaum ib ntawm lawv muaj cov neeg tsav tsheb rau ib taag nqi ntawm $ 124,99, thaum lub lwm yam 20 yog auctions nrog txawv kawg hnub. Tsis tas li ntawd, qhov ua faib muaj ntau shipping nqi, tog twg los $ 7,99 los yog $ 9.99. Nyob rau hauv lwm yam lus, nws yog raws li yog "budgetgolfer" yog khiav thwmsim rau tus neeg tshawb fawb.

Lub faib ntawm lub Taylormade Burner 09 tsav tsheb raug muag los ntawm cov "budgetgolfer" yog ib tug piv txwv ntawm ib tug phim txheej faib, qhov twg lub caij nyoog tib yam khoom yog muag los ntawm cov caij nyoog tib neeg muag khoom, tiam sis txhua lub sij hawm nrog me ntsis txawv yam ntxwv. Nyob rau hauv lub loj heev cav txog eBay muaj cia pua pua txhiab tus sib phim poob lawm uas tsheej lab ntawm faib. Yog li, es muab piv rau cov zaum kawg nqi rau tag nrho cov auctions nyob rau hauv ib muab starting nqi, Einav thiab lug txhawb cov miv ua kev sib piv hauv matched poob lawm. Nyob rau hauv thiaj li yuav muab tau los ntawm cov kev sib piv hauv cov pua pua txhiab tus sib phim poob lawm, Einav thiab lug txhawb cov miv re-qhia cov starting nqi thiab zaum kawg nqi nyob rau hauv cov nqe lus ntawm cov kev siv tus nqi ntawm txhua yam khoom (xws li, nws nruab nrab muag nqi). Piv txwv li, yog hais tias tus Taylormade Burner 09 tsav tsheb muaj ib tug siv tus nqi ntawm $ 100 (raws li nyob rau hauv nws cov kev muag khoom), ces ib tug starting nqi ntawm $ 10 yuav tau qhia raws li 0.1 thiab zaum kawg nqe ntawm $ 120 yuav tau qhia raws li 1.2.

Daim duab 2.6: Ib qho piv txwv ntawm ib tug phim teeb. Qhov no yog lub caij nyoog tib golf qws (ib tug Taylormade Burner 09 tsav tsheb) raug muag los ntawm cov caij nyoog tib neeg ( "budgetgolfer"), tab sis ib txhia ntawm cov muag khoom twb tau sib txawv tej yam kev mob (xws li, sib txawv starting nqi). Daim duab coj los ntawm Einav et al. (2015) .

Rov qab hais tias Einav thiab lug txhawb cov miv twb xav nyob rau hauv cov nyhuv ntawm pib nqi rau auction tau. Ua ntej, siv linear regression lawv kwv yees uas siab dua starting nqi txo qhov yuav tshwm ntawm ib tug muag khoom, thiab hais tias siab dua starting nqi kom zaum kawg muag nqi, zwj ceeb nyob rau ib lub muag tshwm sim. By lawv tus kheej, cov kev kwv yees-uas yog sim tshaj tag nrho cov khoom thiab xav tias ib tug linear kev sib raug zoo ntawm starting nqi thiab zaum kawg tshwm sim-yog tsis yog txhua txhua uas nthuav. Tab sis, Einav thiab lug txhawb cov miv kuj siv tau cov loj heev loj ntawm lawv cov ntaub ntawv mus rau kwv yees ib tug ntau yam ntawm ntau hloov maj mam tshawb pom. Ua ntej, Einav thiab lug txhawb cov miv ua cov kev kwv yees nyias rau cov khoom sib txawv ntawm cov nqi thiab tsis tau siv linear regression. Lawv nrhiav tau tias thaum lub sij hawm sib raug zoo ntawm pib nqi thiab kev kwv yees ntawm ib tug muag yog linear, lub kev sib raug zoo ntawm starting nqi thiab nqi muag yog kom meej meej tsis yog-linear (Daim duab 2.7). Nyob rau hauv kev, rau kev pib nqi ntawm 0.05 thiab 0.85, pib nqi muaj heev me ntsis tej yam rau nqi muag, ib tug nrhiav uas tau ua tiav tsis muaj nyob hauv tus tsom xam uas tau lam xav ib linear kev sib raug zoo.

Xam 2.7: Kev sib raug zoo ntawm auction pib nqi thiab kev kwv yees ntawm ib tug muag (sab laug vaj huam sib luag) thiab nqi muag (txoj cai vaj huam sib luag). Muaj yog roughly ib tug linear kev sib raug zoo ntawm pib nqi thiab kev kwv yees ntawm kev muag khoom, tiam sis yog ib tug uas tsis yog-linear kev sib raug zoo ntawm pib nqi thiab muag nqi; rau pib cov nqi ntawm 0.05 thiab 0.85, pib nqi muaj heev me ntsis tej yam rau nqi muag. Nyob rau hauv ob qho tib si zaum, qhov kev sib raug zoo yog yeej ywj siab ntawm yam khoom muaj nqis. Cov duab cov me nyuam Daim duab 4a thiab 4b Einav et al. (2015) .

Ob, es thaj tshaj tag nrho cov khoom, Einav thiab lug txhawb cov miv kuj siv tau cov loj heev scale ntawm lawv cov ntaub ntawv rau kwv yees tej yam uas pib nqi rau 23 sib txawv pawg ntawm cov khoom (xws li, tus tsiaj cov khoom siv, electronics, thiab kev ua si Memorabilia) (Daim duab 2.8). Cov kev kwv yees qhia tias yog xav paub ntau yus yam khoom xws li Memorabilia-pib nqi muaj ib tug me me ntxim rau cov tshwm sim rau ib muag thiab ib tug loj ntxim rau qhov kawg muag nqi. Ntxiv mus, yog xav paub ntau commodified khoom-xws li DVDs thiab video-pib nqi muaj yuav luag tsis muaj feem nyob rau hauv zaum kawg nqi. Nyob rau hauv lwm yam lus, ib tug nruab nrab uas combines tau los ntawm 23 ntau pawg ntawm cov khoom hides ntaub ntawv tseem ceeb hais txog kev sib txawv ntawm cov khoom no.

Xam 2.8: tau tsom kwv yees los ntawm txhua qeb zuj zus; cov khoom dot nyob rau hauv lub kwv yees rau tag nrho cov pawg yam siv ua ke (Einav et al. 2015, Table 11) . Cov kev kwv yees qhia tias yog xav paub ntau yus yam khoom xws li Memorabilia-pib nqi muaj ib tug me me ntxim rau cov tshwm sim rau ib muag (x-axis) thiab ib tug loj ntxim rau qhov kawg muag nqi (y-axis).

Txawm hais tias koj tsis tshwj xeeb yog xav nyob rau hauv auctions rau eBay, koj yuav tsum qhuas hauv txoj kev uas xam 2.7 thiab daim duab 2.8 lees ib richer to taub ntawm eBay tshaj yooj yooj yim linear regression kev kwv yees uas xav tias linear kev sib raug zoo thiab muab ntau ntau pawg ntawm cov khoom. Cov ntau hloov maj mam kwv piv txwv li lub hwj chim ntawm txoj kev nyob rau hauv loj heev cov ntaub ntawv; cov kwv yuav tau tsis yooj yim sua tsis muaj ib tug enormous tooj ntawm daim teb thwmsim, uas yuav tau prohibitively kim heev.

Ntawm cov hoob kawm, peb yuav tsum muaj tsawg cog qoob loo nyob rau hauv cov kev tshwm sim ntawm tej kev txuam txoj kev tshawb no tshaj peb yuav nyob rau hauv cov kev tshwm sim ntawm ib tug piv xyaum ua tej yam. Thaum nrug muaj feem luj kev tshwm sim los ntawm tej txuam txoj kev tshawb no, muaj ob yam tseem ceeb kev txhawj xeeb. Ua ntej, peb yuav tsum nco ntsoov hais tias peb yuav tsuas xyuas kom meej ncaj ncees kev sib piv rau tej yam uas tau siv rau txuam. Nyob rau hauv lawv lub ntsiab tau, Einav thiab lug txhawb cov miv ho caij nyoog txuam rau plaub yam ntxwv: neeg muag khoom ID naj npawb, yam khoom qeb, yam khoom title, thiab subtitle. Yog hais tias cov khoom yog txawv nyob rau hauv txoj kev uas twb tsis siv rau txuam, uas yuav ua ib tug tsis ncaj ncees kev sib piv. Piv txwv li, yog tias "budgetgolfer" nws txo qis nqi rau Taylormade Burner 09 tsav tsheb nyob rau hauv lub caij ntuj no (thaum golf clubs yog tsawg nrov), ces nws yuav tshwm sim uas qis starting nqi ua rau txo tau kawg tus nqi, thaum nyob rau hauv qhov tseeb qhov no yuav ua tau ib tug yam cuav ntawm raws caij nyoog variation nyob rau hauv coob. Nyob rau hauv Feem ntau, qhov zoo tshaj plaws mus kom ze rau qhov teeb meem no mas yuav tsum tau ua ntau ntau yam ntawm txuam. Piv txwv li, Einav thiab lug txhawb cov miv rov lawv tsom xam qhov twg los piv poob lawm muaj xws li cov khoom ntawm kev muag khoom hauv ib lub xyoo, tsis pub dhau ib lub hlis, thiab contemporaneously. Ua rau lub sij hawm qhov rais tighter txo tus xov tooj ntawm matched poob lawm, tab sis thiaj li txhawj xeeb txog caij nyoog variation. Qhov zoo ces, lawv pom tau hais tias tau yog unchanged los ntawm cov kev hloov no nyob rau hauv txoj kev kev. Nyob rau hauv lub txuam ntaub ntawv, qhov no hom ntawm kev txhawj xeeb no feem ntau yog qhia nyob rau hauv cov nqe lus ntawm observables thiab unobservables, tab sis lub ntsiab lub tswv yim yog tiag tiag uas soj ntsuam ntawm yog tsuas tsim kev ncaj ncees kev sib piv ntawm cov yam ntxwv siv nyob rau hauv txuam.

Qhov thib ob loj kev txhawj xeeb thaum txhais txuam tau yog hais tias lawv tsuas thov rau matched cov ntaub ntawv; lawv tsis thov kom tus neeg mob uas yuav tsis tau sib phim. Piv txwv li, los ntawm limiting cov kev tshawb fawb rau cov khoom uas muaj ntau faib Einav thiab lug txhawb cov miv yog tsom rau kev thiab semi-professional sellers. Yog li, thaum txhais tej kev sib piv peb yuav tsum nco ntsoov hais tias lawv tsuas thov rau qhov no subset ntawm eBay.

Txuam yog ib tug haib zoo rau kev nrhiav ncaj ncees kev sib piv nyob rau hauv loj datasets. Rau ntau cov kev sib raug zaum, piv xav tias zoo li ob-zoo tshaj plaws rau thwmsim, tab sis hais tias yog ib tug ntseeg uas yuav tsum tau kho, me ntsis. Txuam nyob rau hauv loj heev cov ntaub ntawv tej zaum yuav zoo dua ib tug me me muaj pes tsawg tus ntawm daim teb thwmsim thaum: 1) heterogeneity nyob rau hauv los yog ib qho tseem ceeb thiab 2) muaj zoo observables rau txuam. Rooj 2.4 muab ib co lwm yam piv txwv ntawm yuav ua li cas txuam yuav siv tau nrog loj cov ntaub ntawv qhov chaw.

Nyob rau hauv xaus, naïve le caag los kwv yees causal los ntawm uas tsis yog-cov ntaub ntawv yog txaus ntshai. Txawm li cas los, cov tswv yim ua causal kwv dag raws ib pab los ntawm muaj zog rau weakest, thiab soj ntsuam ntawm muaj peev xwm nrhiav tau kev ncaj ncees los sib piv hauv uas tsis yog-cov ntaub ntawv. Cov kev loj hlob ntawm ib txwm-on, loj cov ntaub ntawv systems tsub kom peb muaj peev xwm zoo siv ob uas twb muaj lawm txoj kev: ntuj thwmsim thiab txuam.