Different factors contribute to economic growth. From the perspective of labor resources, there are two primary factors: 1) changes in the amount of labor (jobs and hours) 2) changes in the value of goods and services produced per hour of work (labor productivity). Output growth has come mostly from increases in productivity, rather than hours worked since 2007. Waves of technological change play out differently. It is uncertain how the next wave might further boost productivity and the extent to which those gains might result in rising compensation for workers.