Since the 1970s there has been a large number of countries that combine
formal democratic institutions with authoritarian practices. Although in such
countries the ruling elites may receive considerable voter support they often
employ several manipulation tools to control election outcomes. A common
practice of these regimes is the coercion and mobilization of a significant
amount of voters to guarantee the electoral victory. This electoral
irregularity is known as voter rigging, distinguishing it from vote rigging,
which involves ballot stuffing or stealing. Here we develop a statistical test
to quantify to which extent the results of a particular election display traces
of voter rigging. Our key hypothesis is that small polling stations are more
susceptible to voter rigging, because it is easier to identify opposing
individuals, there are less eye witnesses, and supposedly less visits from
election observers. We devise a general statistical method for testing whether
voting behavior in small polling stations is significantly different from the
behavior of their neighbor stations in a way that is consistent with the
widespread occurrence of voter rigging. Based on a comparative analysis, the
method enables to rule out whether observed differences in voting behavior
might be explained by geographic heterogeneities in vote preferences. We
analyze 21 elections in ten different countries and find significant anomalies
compatible with voter rigging in Russia from 2007-2011, in Venezuela from
2006-2013, and in Uganda 2011. Particularly disturbing is the case of Venezuela
where these distortions have been outcome-determinative in the 2013
presidential elections
