A first-digit anomaly in the 2009 Iranian presidential election

Abstract

A local bootstrap method is proposed for the analysis of electoral vote-count first-digit frequencies, complementing the Benford's Law limit. The method is calibrated on five presidential-election first rounds (2002--2006) and applied to the 2009 Iranian presidential-election first round. Candidate K has a highly significant (p< 0.15%) excess of vote counts starting with the digit 7. This leads to other anomalies, two of which are individually significant at p\sim 0.1%, and one at p\sim 1%. Independently, Iranian pre-election opinion polls significantly reject the official results unless the five polls favouring candidate A are considered alone. If the latter represent normalised data and a linear, least-squares, equal-weighted fit is used, then either candidates R and K suffered a sudden, dramatic (70%\pm 15%) loss of electoral support just prior to the election, or the official results are rejected (p\sim 0.01%).

36 pages, 19 figures, 11 tables; v2: 3 of 6 biggest cities satisfy K7; v3: simulations give p=0.0007, K7a distribution is odd; v4: more conservative simulation method, pre-election polls analysis added; v5: discussion of election validity claims; v6: minor corrections

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