It is rather arguable whether it is because people who plan tend to end up well, or people who make more money tend to have more time or resource to proper financial planning.

The simple act of planning - calculating a retirement target, say, or estimating how much you should save - has a surprisingly large impact on your odds of success.

Consider the results of a study by Annamaria Lusardi, a professor of economics at Dartmouth College, and Olivia Mitchell, a professor of insurance and risk management at the University of Pennsylvania and executive director of the Pension Research Council.

Analyzing data from a 2004 national survey on the first wave of baby boomers, Lusardi and Mitchell found that those who did "a lot" of retirement preparation had a median net worth of $200,000, compared with $84,000 for those who did the least.

"Even a small amount of planning can make a huge difference," says Lusardi. Those who did "a little" were also ahead, with a median net worth of $172,000. Planning pays off because it's a crucial psychological trigger. Studies show that writing a plan down - or even simply thinking about it - greatly increases the likelihood that you will follow through.