http://www.usatoday.com/money/perfi/columnist/krantz/2005-12-02-presidents_x.htm
Q: Has the stock market been better, on average, when a Republican or Democrat has been in office? Do you have a chart that shows this?
A: Many investors assume that Republican presidents are better for the stock market. That's not true.
But before I get to the particulars, a disclaimer: This answer is not a political statement. By answering this question, I am merely conveying the cold, hard facts regarding stock price performance under both Republicans and Democrats. I endorse no political party and have no vested interest in the results.
To get the answer to your question, I turned to the respected Stock Trader's Almanac by Yale and Jeffrey Hirsch. This book tracks and organizes historical facts about the stock market, and the 2005 edition addresses your question on page 42.
Using the Dow Jones industrial average as the benchmark, Stock Trader's Almanac shows a $10,000 investment compounded during Democratic presidencies since 1901 would be worth $279,705 after 48 years. The same $10,000 investment during 56 Republican years would have been worth just $78,699. If you adjust for inflation, the value of a $10,000 investment under Democratic presidents is $33,426.The inflation-adjusted value under Republican presidents is $26,145.
Many factors affect these results besides the president's party. The Republicans got a big lift during the Eisenhower and Reagan years. Democrats Roosevelt and Truman benefited from the recovery that followed the 89% fall in the Dow during the Depression. The Democratic lead was solidified by the tremendous run-up in stocks during the Clinton administration.
If these types of statistics interest you, I really suggest you pick up a copy of Stock Trader's Almanac. The book contains hundreds of fascinating historical records spotting trends and patterns in the stock market.
also....
http://www.slate.com/default.aspx?id=2071929