Source: Uber. Data aggregated at the driver-partner-week level. Figures exclude incentive payments that are offered to new driver-partners in some markets. Earnings are net of Uber’s fees but do not adjust for driver-partners’ expenses. Final line reflects the 20 survey markets in the 2014 BSG surveys. Cities weighted by their trip distributions in October 2014. In the combined set of 20 areas, more than half of uberX driver-partners chose to drive for 15 hours or less a week, and fully 83 percent chose to drive less than 35 hours a week.22 Yet the largest difference in hourly earnings across workers in the various hours categories was $0.66 (about four percent) between those driver-partners driving 16 to 34 hours a week and those driving one to 15 hours a week. Across all uberX drivers, earnings per hour each week are negatively correlated with hours logged with the app on that week, although this negative correlation may partly be a statistical artifact of the imprecision in measuring hours, as noise in hours will tend to induce a negative correlation due to division bias. A regression that instruments for hours worked in week t using hours worked during week t-1 found no evidence of an effect of hours worked on hourly earnings. In any event, there is little evidence that uberX drivers who work longer hours per week earn more per hour than those who work shorter hours, which may make the platform particularly attractive to those interested in working short hours. Figure 7 shows the distribution of weekly hours with the app turn on over time for all Uber drivers combined. As Uber has expanded over time, more and more driver-partners are utilizing the platform for 15 hours or less per week, while the percentage of those on the platform for more than 35 hours a week has declined. This is partly a result of the fact that uberX grew more rapidly than UberBLACK drivers, and uberX drivers tend to drive less per week. 22 Driver-partners who provided service on both UberX and UberBLACK during the course of October 2015 are excluded from Table 3. Drivers who utilized the UberBlack platform tended to log longer hours per week than UberX drivers: 52 percent of UberBlack drivers used the platform for 35 hours or more a week. 21