“Is it better to delay and get fewer years of higher income, or start early and get more years of lower income?” First, make sure you understand how Social Security benefits are calculated. Next estimate your expected longevity with a couple online calculators. Are you better off claiming benefits on your own record or your spouse’s (or ex-spouse’s) earnings history? Bradford M. Pine explains: “Every year you delay taking benefits ‘earns’ you 8% in additional Social Security income in the future.”
http://www.kiplinger.com/article/retirement/T051-C032-S014-social-security-delay-or-hit-go.html
Also, read: How well do you know Social Security? http://www.kiplinger.com/quiz/retirement/T051-S001-how-well-do-you-know-social-security/index.html
Source: Financial Planning for Women