Oh, you are just asking for the rate at which long term capital gains are taxed?  15% (for most, from 0% to 28% for others)
 - http://www.irs.gov/newsroom/article/0,,id=106799,00.html
 - http://en.wikipedia.org/wiki/Capital_gains_tax#United_States
 - http://www.bankrate.com/finance/money-guides/capital-gains-tax-rates-1.aspx