Every day we engage in behaviors that raise or lower our long-term chances for survival. Smoke cigarettes and you increase your risk of dying prematurely. Exercise and eat vegetables and you are likely to add precious time to your existence. But just how bad or good are those and other activities, such as drinking alcohol? David Spiegelhalter , a professor of risk assessment at the University of Cambridge, has converted reams of statistical tables into a simple metric: a microlife --30 minutes. If you smoke two cigarettes, you lose 30 minutes of your life. If you exercise for 20 minutes you gain an hour. The risks are explained in our January 2013 Graphic Science column.