Nobody's life, liberty or property is safe while Congress is in session

Looks like this phrase is more than just part of the slogan of a popular website, according to research by Michael Ferguson and Hugh Witte, Congress and the Stock Market. Here's the abstract:

We find a strong link between Congressional activity and stock market returns that persists even after controlling for known daily return anomalies. Stock returns are lower and volatility is higher when Congress is in session. This is consistent with firms facing a more uncertain tax and regulatory environment when Congress is in session. This "Congressional Effect" can be quite large - about 90% of the capital gains over the life of the DJIA have come on days when Congress is out of session. The Effect varies systematically with the public's opinion of Congress: returns are lower and volatility higher when a relatively unpopular Congress is in session. This suggests investors evaluate Congressional activity through time and adjust their expectations accordingly.