Figure 7: Distribution of Uber Driver-Partner Hours Over Time Note: Sample consists of all U.S. uberX and UberBlack driver-partners spending at least an hour online in a given week in 20 BSG US cities surveyed in 2014. Figure 8 likewise provides an analysis of driver earnings over time. Specifically, for each city we calculated the 1-percent trimmed mean, and then computed a fix-weighted average across cities to hold constant shifts across cities. Driver-partner earnings fluctuate from week to week, but in the 20 markets in the 2014 BSG survey, the average was $20.19 from June 2014 through October 2015. A regression of hourly earnings on time found no evidence of a time trend. The fact that fares have trended down while hourly earnings display no time trend suggests that hourly earnings are anchored to the drivers’ alternative wages, with the entry and exit of workers causing utilization rates to adjust to clear the market at a more or less fixed wage.23 23 Hsieh and Moretti (2003) reach a related conclusion concerning the earnings of real estate agents, namely that entry and exit of real estate agents leads their real earnings to be invariant to fluctuations in housing prices. 22