Interesting -- and not at all surprising.

Quoted: In Daniel Gilbert's 2006 book "Stumbling on Happiness," the Harvard professor of psychology looks at several studies and concludes that marital satisfaction decreases dramatically after the birth of the first child—and increases only when the last child has left home. He also ascertains that parents are happier grocery shopping and even sleeping than spending time with their kids. Other data cited by 2008's "Gross National Happiness" author, Arthur C. Brooks, finds that parents are about 7 percentage points less likely to report being happy than the childless.