The practice of tipping is one of the most irrational, un-economic behaviors we engage in. It’s not in our economic best-interest to tip; essentially we do it because it’s a social norm — a nicety. In this episode of Freakonomics Radio, Stephen Dubner looks at why we tip, what kinds of things can nudge tips upward, and what’s wrong with tipping overall. In the end, we wonder whether or not the practice of tipping should be eliminated altogether. Research shows that African American waiters make less in tips than people of other races, so tipping is a discriminatory practice. Later in the hour: if your parent has the gene for Huntington’s disease you have a 50% chance of getting it yourself. Huntington’s is a debilitating fatal disorder. People can do genetic testing to see if they will fall ill, yet only 5% of people choose to do so. Stephen Dubner talks to University of Chicago economist Emily Oster about her research on Huntington’s genetic testing, and the value of not knowing your fate.