NATIONAL BUREAU OF ECONOMIC RESEARCH
NATIONAL BUREAU OF ECONOMIC RESEARCH

NBER Working Papers by Philip S. Babcock

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Working Papers

January 2011Letting Down the Team? Evidence of Social Effects of Team Incentives
with Kelly Bedard, Gary Charness, John Hartman, Heather Royer: w16687
This paper estimates social effects of incentivizing people in teams. In two field experiments featuring exogenous team formation and opportunities for repeated social interactions, we find large team effects that operate through social channels. The team compensation system induced agents to choose effort as if they valued a marginal dollar of compensation for their teammate from two-thirds as much (in one study) to twice as much as they valued a dollar of their own compensation (in the other study). We conclude that social effects of monetary team incentives exist and can induce effort at lower cost than through direct individual payment.
December 2010Networks and Workouts: Treatment Size and Status Specific Peer Effects in a Randomized Field Experiment
with John L. Hartman: w16581
This paper estimates treatment size and status specific peer effects that are not detected by widely-used approaches to the estimation of spillovers. In a field experiment using university students, we find that subjects who have been incentivized to exercise increase gym usage more if they have more treated friends. However, control subjects are not influenced by their peers. Findings demonstrate that fraction treated has a large influence on outcomes in this environment, and spillovers vary greatly by treatment status. Results highlight subtle effects of randomization and document a low-cost method for improving the generalizability of controlled interventions in networked environments.
April 2010The Falling Time Cost of College: Evidence from Half a Century of Time Use Data
with Mindy Marks: w15954
Using multiple datasets from different time periods, we document declines in academic time investment by full-time college students in the United States between 1961 and 2003. Full-time students allocated 40 hours per week toward class and studying in 1961, whereas by 2003 they were investing about 27 hours per week. Declines were extremely broad-based, and are not easily accounted for by framing effects, work or major choices, or compositional changes in students or schools. We conclude that there have been substantial changes over time in the quantity or manner of human capital production on college campuses.

Published: Philip Babcock & Mindy Marks, 2011. "The Falling Time Cost of College: Evidence from Half a Century of Time Use Data," The Review of Economics and Statistics, MIT Press, vol. 93(2), pages 468-478, December. citation courtesy of

March 2009Reduced-Class Distinctions: Effort, Ability, and the Education Production Function
with Julian R. Betts: w14777
Do smaller classes boost achievement mainly by helping teachers impart specific academic skills to students with low academic achievement? Or do they do so primarily by helping teachers engage poorly behaving students? The analysis uses the grade 3 to 4 transition in San Diego Unified School District as a source of exogenous variation in class size (given a California law funding small classes until grade 3). Grade 1 report cards allow separate identification of low-effort and low-achieving students. Results indicate that elicitation of effort or engagement, rather than the teaching of specific skills, may be the dominant channel by which small classes influence disadvantaged students.

Published: Babcock, Philip & Betts, Julian R., 2009. "Reduced-class distinctions: Effort, ability, and the education production function," Journal of Urban Economics, Elsevier, vol. 65(3), pages 314-322, May. citation courtesy of

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