> For an individual woman in her 50s, then, annual mammograms may catch breast cancer, but they reduce the risk of dying of the disease over the next 10 years by only .07 percentage points — from .53 percent to .46 percent. Reductions for women in their 40s are even smaller, from .35 percent to .3 percent.

Many people are going to be baffled by risk presented like this. Presenting the numbers differently is helpful to let people understand the risks.

"Imagine 10,000 women like you. Of those X will die from this disease. But if we take those same 10,000 women and give them mammograms we find that Y will die from the disease".

Sometimes X will be 2 and Y will be 1 (50% decrease in risk) or X will be 100 and Y will be 2 or X will be 100 and Y will be 99.

Presenting the numbers this way allows most people to understand the risks better.