Enikolopov et al "Field experiment estimate of electoral fraud in Russian parliamentary elections"
"To examine the effect of observers on the distribution of vote shares for United Russia, we combined univariate kernel density estimations of the vote share for United Russia for polling stations from these three groups with corresponding histograms (Fig. 2). For the polling stations in the control group, the distribution is bimodal with two peaks: one around 25% of votes and another one around 55% of votes. The distribution for polling stations in the treatment group also has two peaks, with the first one around 25% of votes. However, the second mode is located around 50% of votes and the share of polling stations around this peak is noticeably smaller compared with the control group. For the polling stations in the treatment group in which no violations were reported by observers, the distribution becomes unimodal, with the peak around 25% of votes for United Russia. Thus, the results are consistent with the hypothesis that the distribution of vote shares for United Russia in the control group is a mixture of two distributions that correspond to polling stations without electoral fraud (for which the distribution was centered around 25% of votes) and polling stations with electoral fraud (for which the distribution was centered around 55% of votes). A similar pattern is observed in the distribution of the turnout, but not in the distribution of vote shares for the other parties. (Fig. S1 shows similar graphs for the distributions of vote shares of other parties and turnout for the same three groups of polling stations. Vote shares of other parties without observers demonstrate fatter left tails, in contrast to symmetric densities in the no-violation case, consistent with hypotheses that votes were stolen from these parties and added to votes of United Russia.) "
Вывод из этой работы (в части, относящейста к распределениям) IMHO состоит в том, что там где наблюдателями были зафиксированы нарушания, таки были нарушения. Нужен ли кому-либо статистический анализ для того, чтобы сделать такой вывод?