how to calculate the "income_mean"=second one /first one, by citycode_s!
for example，citycode_s 1100 ，income_mean= 57322.33389722986/33682.35625664658; citycode_s 1200 ，income_mean=40325.102739726026/29753.190959409592. and so on !


* Example generated by -dataex-. To install: ssc install dataex
clear
input int citycode_s double(income_mean theil12)
1100 33682.35625664658 -.09457062183299848
1100 57322.33389722986 .12391108340038566
1200 29753.190959409592 -.05872110854249861
1200 40325.102739726026 .06846042765325541
1301 22297.040100250626 -.04969700128548113
1301 30239.176305970148 .057990392047033434
1302 25453.37556561086 -.03710634711066719
1302 31722.322580645163 .04146771925221664
1303 20534.944444444445 -.03252622921476144
1303 24075.134920634922 .03523220062662236
1304 18029.75581395349 -.033660199599665125
1304 24278.64096385542 .03916057514007405
1305 12509.309322033898 -.11158525928692456
1305 21411.909465020577 .14624650171799183
1306 18911.112359550563 -.08633127861917259
1306 28511.696145124715 .10615709166595672
1307 19450.059701492537 -.020646009633556964
1307 22214.921161825725 .022074235690224132
1308 21092.596153846152 -.024475475093113402
1308 24155.725352112677 .026202284626273616
1309 15338.456621004567 -.08366154860663896
1309 23577.881656804733 .10397568086796262
1310 18677.83486238532 -.07094961031125857
1310 26399.896341463416 .08446930691617059
end
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