The authors wish to thank Sheri Berman, Mirella Eberts, Anna Grzymala-Busse, Padraic Kenney, Roger Petersen, Waldemar Skrobacki, Tim Snyder; the participants in seminars at the University of Wisconsin at Madison's Getting into Numbers working group, the Laboratory in Comparative Ethnic Processes, Duke University, Harvard University, University of California at Los Angeles, the University of Washington; and three readers for SlavicReview for comments on earlier drafts of this article. This research has been supported in part by a generous grant from the National Science Foundation (SES-0217499). Jason Wittenberg also acknowledges the support of the Harvard Academy for International and Area Studies.

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14 More formally, for every district i, , where is the percentage of non-Catholics supporting communist parties, V_t is the communists' percentage of the vote, C_i, is the percentage of Catholics in the population, and is the percentage of Catholics supporting communist parties.

15 More specifically, and are drawn from a truncated bivariate normal distribution. The peak of the distribution is centered where the line intersections are the densest. El's allowance for parameter variation is one of the features that distinguishes it from such popular ecological regression techniques as Goodman's regression. See Goodman, Leo, “Some Alternatives to Ecological Correlation,” American Journal of Sociology 64, no. 6 (May 1959): 610–24CrossRefGoogle Scholar.

16 For details of the EI method and the statistical assumptions underlying it, see King, A Solution to the Ecological Inference Problem. For a shorter overview of EI and some alternatives, see Palmquist, Bradley, “Unlocking the Aggregate Data Past—Which Key Fits?“ Historical Methods 34, no. 4 (Fall 2001): 159–69CrossRefGoogle Scholar.

17 On the reconstitution of the Polish state, see Antony Polonsky, Politics in IndependentPoland (Oxford, 1972), chap. l;Jerzy Holzer, Mozaika polityana drugiej neczypospolitej (Warsaw, 1974); Holzer, , Polska to pienuszej wojnie swiatowej (Warsaw, 1967)Google Scholar.

18 See the commentary from the first Polish Census of 1921, Statystyka Polski Serja C (Warsaw, 1923-27).

19 Reprinted and translated in Horak, Stephan, Poland and Her National Minorities,1919-1939 (New York, 1961), 196 Google Scholar.

20 For a partisan but still informative survey, see Mornik, Stanislaus, Potens Kampfgegen seine nichtpolnischen Volksgruppen (Berlin, 1931)Google Scholar.

21 According to Horak's account, which is sympathetic to the Ukrainian national cause, by spring 1923 “the majority of [the] Galician-Ukrainian population [had] resigned themselves to Polish supremacy. The Ukrainian political parties decided to continue the struggle for national rights on the floor of the Sejm and to stress the desire for independence, even when the dark clouds of Polish domination had not completely descended over the Ukraine.” Horak, Poland and Her National Minorities, 59.

22 Jerzy Tomaszewski, “Robotnicy Bialorusini w latach 1919-1938 w Polsce,” ActaBaltico Slavica, 1967, no. 5:95-112; Tomaszewski, , “The National Structure of the Working Class in the South-Eastern Part of Poland 1921-1939,” Acta Poloniae Hislorica, 1968, no. 19:89–111 Google Scholar; Landau, Zbigniew and Tomaszewski, Jerzy, Robotnicy przemystowi w Polsce: Materialnewarunki bytu 1918-1939 (Warsaw, 1971), 95 Google Scholar.

23 Tomaszewski, Jerzy, Rzeczpospolita xirielu narodów (Warsaw, 1985), 25–37 Google Scholar.

24 Miscategorizing Catholic Lithuanians would be a serious problem if we were attempting to estimate their voting behavior, but since we do not do this in this article, it does not affect our analysis.

25 See Falski, Marjan, Wyniki spisu dzieci z aenuca 1926 roku w zastosoivaniu do badaniapotrzeb szkolnictwa powszechnego (Warsaw, 1928)Google Scholar.

26 From the standpoint of international law, the borders had been more or less settled by the Treaty of Riga in 1921 and by the 15 March 1923 Council of Ambassadors’ full recognition of Polish sovereignty over eastern Galicia in reference to the (June 1919) Minorities Treaty. Notwithstanding this recognition, it appears drat many Ukrainians held out the hope that the status of eastern Galicia (or, as the Ukrainians preferred, western Ukraine) might someday be revisited by the League of Nations.

27 Such a method has been proposed by Rosen, Ori, Jiang, Wenxin, King, Gary, and Tanner, Martin A., “Bayesian and Frequentist Inference for Ecological Inference: The RXC Case,” Statistica Nederlandica 55, no. 2 (2001): 134–56CrossRefGoogle Scholar. But this technique places much greater demands on the data, since many more parameters have to be estimated. It is not feasible at the district level, though it would be possible if the data were disaggregated by settlement. We are currently gathering these data.

28 Jews and Catholics dwelled throughout interwar Poland, so the estimates for these groups were computed using the full database wherever possible. In some cases, due to lack of data, western districts are excluded. The Ukrainian estimates are based on Galician districts, and the Orthodox on eastern, or eastern and central districts, depending on the availability of observations and the stability of the estimates. In no case were there significant discrepancies between estimates derived just from eastern districts and those attained by combining eastern and central districts. We compensated for the Ukrainian boycott of the 1922 election by using EI to estimate the turnout rate among Ukrainians for each district and by weighting the census data by the estimated turnout. The estimates of minority support for the Right were obtained using the proportion of the district population that was Catholic as a covariate.

29 Hereafter by “Ukrainians” we mean Galician (Uniate) Ukrainians, unless specifically noted otherwise.

30 See Polonsky, Politics in Independent Poland, 139-40.

31 A large portion of this vote in western Poland probably came from German Catholics.

32 On the origins and consequences of Poland's interwar institutional choices, see Bernhard, Michael, “Institutional Choice and the Failure of Democracy: The Case of Interwar Poland,” East European Politics and Societies 13, no. 1 (Winter 1999): 35–59 Google Scholar.

33 It is true, however, that the nonparty Sikorski government received support from both Ukrainian and Belarusan parties, an important indication of the potential for intereuinic cooperation in interwar Poland.

34 Cycles of discrimination, repression, and violence plagued both eastern Galicia and Poland's eastern territories throughout the mid-to-late 1920s. See Felinski, M., TheUkrainians in Poland (London, 1931)Google Scholar. Soviet propaganda was especially effective among Belarusans; see Vakar, Nicholas P., Belorussia: The Making of a Nation (Cambridge Mass., 1956), 125–27CrossRefGoogle Scholar.

35 Rothschild, Joseph, Pilsudski's Coup d'Etat (New York, 1966)Google Scholar.

36 Ibid.

37 The Communist Party had been outlawed in 1924 but its adherents continued to run in a number of front organizations that are widely identifiable in the literature on the interwar period. An extensive analysis of these front organizations is undertaken for eastern Poland in Radziejowski, The Communist Party of Western Ukraine.

38 As before, Jewish and Catholic estimates are obtained using the full database whenever possible. The estimates of Jewish support for the right pertain only to Galicia and central Poland, and estimates of Jewish support for the nonrevolutionary left pertain only to eastern and central Poland. Orthodox estimates pertain only to the eastern or eastern and central districts, and (Galician) Ukrainian only to the south.

39 Holzer, Mozaikapolityczna, 254-58; Tomaszewski, Rzecipospolita mielu, 105-34.

40 Note also that, as in table 2, the row percentages do not add up to 100 percent, reflecting estimation error. For details, see the discussion following table 2.

41 Łuck, Równe, Krzemieniec, Dubno, Kamień-Koszyrski, and Sarny. These districts were all between 70 and 80 percent Ukrainian Orthodox. The Communists also did better than average in several disproportionately Orthodox Ukrainian districts in and around Chelm.

42 According to Vakar, between 1925 and 1928 the Soviet-supported Belarusan Peasants' and Workers’ Association, the Rabotnickaja Hramada, enrolled over 100,000 members from all social classes in eastern Poland. See Vakar, Belorussia, 126.

43 It is, of course, important to condition this interpretation on differences in socioeconomic structure across districts. We leave this for future research.

44 On Galician Ukrainian national identity, see the relevant essays in Markovits, Andrei S. and Sysyn, Frank E., eds., Nationbuilding and the Politics of Nationalism: Essays onAustrian Galicia (Cambridge, Mass., 1982)Google Scholar; also Keely Stauter-Halsted, The Nation in the Village:The Genesis of Peasant National Identity in Austrian Poland, 1848-1914 (Ithaca, 2001); Himka, John-Paul, Religion and Nationality in Western Ukraine: The Greek Catholic Church andthe Ruthenian National Movement in Galicia, 1867-1900 (Montreal, 1999)Google Scholar. On the settlement structure of Ukrainians within Galicia, see Tomaszewski, “National Structure.” On the Ukrainian National Movement, see Magocsi, Paul Robert, A History of Ukraine (Seattle, 1996), 351–84, 436-59Google Scholar; Subtelny, Orest, Ukraine: A History (Toronto, 2000), 201–335 Google Scholar. On Belarusans, see Vakar, Belorussia, 1-92.

45 Horak hints at this as well. Horak, Poland and Her National Minorities, 59.

46 The book that provides much of the “evidence” for this assertion, not only at the organizational but also at the mass level, is the frequently cited account of Regula, Jan Alfred, Historja Komunistycznej Partji Polski w świetle faktów i dokumentów (Warsaw, 1934)Google Scholar.

47 This is how Rogers Brubaker characterizes interwar Poland; see Brubaker, , NationalismReframed: Nationhood and the National Question in the New Europe (Cambridge Eng., 1996), 84 CrossRefGoogle Scholar.

48 Hirschman, Albert O., Exit, Voice, and Loyalty: Responses to Decline in Firms, Organizations,and States (Cambridge, Mass., 1970)Google Scholar.

49 For a fascinating discussion of Poland's Jewish Communists, see Schatz, Jaff, TheGeneration: The Rise andFall ofthejewish Communists of Poland (Berkeley, 1991)Google Scholar.

50 Gerrits, “Antisemitism,” 49.