Senators' investments beat the Standard & Poor's 500 by an average 12 percent a year from 1993 to 1998, according to the study by Alan J. Ziobrowski of Georgia State University and colleagues at three other schools. The study found that during the boom years of 1993-98, a majority of US Senators were trading stocks - and beating the market by 12 percentage points a year on average. By comparison, corporate insiders beat the market by 5 percent, and typical households underperformed by 1.4 percent.
There is a consistent rise in stock prices in the month prior to the announcement date, but with hundreds of takeovers every year, prosecutions on this score happen every couple of years only, and usually because the pigs got into options, where their activity really stuck out.
Prior to the 9/11 attacks, there was unusually heavy activity in airline put options the week prior, and yet, no arrests made.