Does welfare spending reduce the poverty rate?

The Federalist reports Tom Coburn:

However, they are probably less inclined to concede that the constant growth of the welfare state produces inversely diminishing returns. “In 1966 when the massive means-tested entitlements to address the poor began, the overall poverty rate in the United States was 14.7 percent,” Coburn notes. “In 2013, and more than $15 trillion later, the poverty rate was measured at 14.5 percent. That could be a statistical error, rather than even this miniscule 0.2 percent decline.”

$15 trillion for 0.2% decline!