Source: Haishan Yuan, American Law and Economics Review, Advance Access, First published online: February 26, 2015
From the abstract:
The Bipartisan Campaign Reform Act of 2002 addressed two issues, soft money and independent expenditures on issue ads for electoral advocacy. The Supreme Court initially upheld most provisions in 2003 but subsequently weakened and struck down provisions on independent expenditures. I examine the stock value of firms with a long history of campaign contributions around the key developments of three Supreme Court cases. Stock prices of contributing firms react positively to Court events associated with campaign finance deregulation. It implies that the average rates of return to these rights of political spending are between 1 and 2% of stock values.