Is it customary to reveal a decade of tax returns?
The high-water mark for disclosure was 30 years, set by Sen. Robert Dole, R-Kan., in the 1996 election. Second-place honors go to Sen. John Kerry, D-Mass., for providing 20 years' worth when he ran in 2004, although he had released 15 of those returns before his presidential bid.
After that, there is a tie between Romney's father, George Romney, in 1968 and Bill Clinton in 1992. Both released 12 years of tax returns. Close behind is Sen. John Edwards, D-N.C., with 10 when he was Kerry's running mate.
Several candidates released anywhere from six to nine years of tax returns. In 2000, George W. Bush provided nine, and Al Gore provided eight. In the 2008 primary, then-Sen. Barack Obama, D-Ill., delivered seven, a move that was matched by Hillary Rodham Clinton about a month later. In 1988, Massachusetts Gov. Michael Dukakis released six years of returns.