The WSJ blog reports that:
audits for the wealthy surged in 2010. Among taxpayers who reported $10 million or more in income in 2010, more than 18% were audited. That is up 80% from 2009, when only 10% were audited, and in 2008, when 9% were audited.
The rates were higher for other high-income taxpayers, too. The report showed that among taxpayers who reported $5 million to $10 million in income, nearly 12% were audited, compared with 6% in 2008. For those earning $1 million to $5 million, audits rose to 7% in 2010 from 4% in 2008.
Still, the $10 million or more crowd–which represented .01% of all returns–is clearly the fattest target, since that is where the money is.