that a shift in labor force distribution from higher-productivity-growth manufacturing to lower-productivity-growth services decreases the rate of economic growth in the long run. Likewise, the economists Jochen Hartwig and Hagen Krämer concluded in a 2019 paper that, while Outlon's theory is "logically consistent", it is "not in line with the data", which shows a lowering of aggregate productivity growth. Education The Baumol effect has been applied to the education sector, including by Baumol himself. By most measures, productivity growth in the education sector over the last several decades has been low or even negative; the average student-teacher ratio in American universities, for instance, was sixteen to one in 2011, just as it was in 1981. Yet, over this period, tuition costs have risen substantially. It has been proposed that this is at least partially explained by the Baumol effect: even though there has been little or even negative productivity growth in the education sector, because of productivity increases across other sectors of the economy universities today would not be able to attract professors with 1980s-level salaries, so they are forced to raise wages to maintain their workforce. To afford the increased labor costs, universities raise tuition (i.e. they increase prices). Evidence on the role of the Baumol effect in rising education costs has been mixed. Economists Robert B. Archibald and David H. Feldman, both of the College of William & Mary, argued in a 2006 study, for instance, that the Baumol effect is the dominant driver behind increasing higher education costs. Other studies, however, have found a lesser role for the Baumol effect. In a 2014 study, the economists Robert E. Martin and Carter Hill devised a model that determined that the Baumol effect explained only 23%–32% of the rise in higher education costs. The economists Gary Rhoades and Joanna Frye went further in a 2015 study and argued that the Baumol effect could not explain rising tuition costs at all, as "relative academic labor costs have gone down as tuition has gone up". The cost disease may also have only limited effects on primary and secondary education: a 2016 study on per-pupil public education spending by Manabu Nose, an economist at the International Monetary Fund, found that "the contribution of Baumol's effect was much smaller than implied by theory"; Nose argued that it was instead rising wage premiums paid for teachers in excess of market wages that were the