Artículos de revistas
Quick Anomaly Detection by the Newcomb–Benford Law, with Applications to Electoral Processes Data from the USA, Puerto Rico and Venezuela
Autor
Torres, David
Pericchi Guerra, Luis R.
Institución
Resumen
A simple and quick general test to screen for numerical anomalies
is presented. It can be applied, for example, to electoral processes,
both electronic and manual. It uses vote counts in officially published voting
units, which are typically widely available and institutionally backed.
The test examines the frequencies of digits on voting counts and rests on the
First (NBL1) and Second Digit Newcomb–Benford Law (NBL2), and in a
novel generalization of the law under restrictions of the maximum number
of voters per unit (RNBL2). We apply the test to the 2004 USA presidential
elections, the Puerto Rico (1996, 2000 and 2004) governor elections, the
2004 Venezuelan presidential recall referendum (RRP) and the previous 2000
Venezuelan Presidential election. The NBL2 is compellingly rejected only in
the Venezuelan referendum and only for electronic voting units. Our original
suggestion on the RRP (Pericchi and Torres, 2004) was criticized by The
Carter Center report (2005). Acknowledging this, Mebane (2006) and The
Economist (US) (2007) presented voting models and case studies in favor
of NBL2. Further evidence is presented here. Moreover, under the RNBL2,
Mebane’s voting models are valid under wider conditions. The adequacy of
the law is assessed through Bayes Factors (and corrections of p-values) instead
of significance testing, since for large sample sizes and fixed α levels
the null hypothesis is over rejected. Our tests are extremely simple and can
become a standard screening that a fair electoral process should pass. NSF Grants 0604896 and 0630927