Randall Lewis

October 12, 2011


Dr. Randall Lewis is a 2006 graduate of Brigham Young University with degrees in both economics and mathematics. Dr. Lewis received his PhD from the Massachusetts Institute of Technology in 2010 with his fields of concentration being industrial organization and econometrics. While working toward his PhD, Dr. Lewis began working as an Economic Research Scientist for Yahoo! Research, where he is still currently employed. Dr. Lewis has been honored with various awards, including BYU’s Department of Economics Valedictorian and MIT Presidential Fellow in 2006 and Yahoo! Superstar Nominations in 2010 and 2011. At Yahoo! Research, Dr. Randall focuses on statistical measurement using econometrics and casual statistics to learn valuable insights from large data sets. He enjoys working on a variety of research fields ranging from the econometrics of social networks to large scale field experiments. Dr. Lewis has primarily focused his skills on measuring the impact of online display and search advertising on important business outcomes such as clicks, page views, searches, survey outcomes, and both online and offline (in-store) sales.


Yahoo! Research partnered with a nationwide retailer to study the effectiveness of display advertising on online and in-store sales on more than three million shared customers. We measure the impact of higher ad impression frequency using a simple design that varies the ads that users see on the Yahoo! network within identically targeted campaigns: users in the treatment group see the retailer’s ads; users in the control group see unrelated, `control’ ads; and users in the half treatment group see an equal probability mixture of the retailer’s and control ads. We find a statistically significant increase in sales, relative to the control group, as a result of the ads. Doubling the number of impressions per person–from 17 to 34 in a two-week period–approximately doubled the treatment effect. We also find striking evidence that the ads most strongly affected customers who live closest to the retailer’s brick-and-mortar locations: those who live within two miles of a store experience more than ten times the incremental sales lift due to ads as those who live farther away.