# To Insure Promptness

Paper finds that <a href="http://papers.ssrn.com/sol3/papers.cfm?abstract_id=401201">white taxi passengers tip more than black passengers</a>. Gee, that's interesting, I thought, I wonder how they're controlling for income? ... as it happens, they don't ("What we attribute to passenger race may be caused at least in part by a tendency of poorer people to tip less") even though the median income of blacks in New Haven, Connecticut, is <a href="http://www.epodunk.com/cgi-bin/incomeOverview.php?locIndex=9218">65% of that of whites</a>. (See also weak defense on page 33ff.)