total fixed costs for developing the assessment program from its costs of other activities. J-PAL Africa’s fixed cost for developing the certification program on top of the assessment program was approximately USD 17,685 or USD 7.87 per candidate who received the public certification intervention. This covered J-PAL Africa staff costs during development and all costs of piloting the certificates with firms and workseekers. This includes the cost of developing and piloting the private and placebo certifications, which we cannot easily separate from the public certification, but excludes the costs of developing and piloting the audit study and firm-facing experiments.

We compare these average costs to the average benefit per participant who received the public certification intervention over the first three months after the intervention. Public certification increases average earnings by USD 9.05 in the week before the endline survey and the endline survey occurred on average 14.4 weeks after treatment. Multiplying these together gives an average effect on earnings since treatment of USD 130.2: 5.6 times higher than the average variable cost of certification, 2.3 times higher than the average variable cost of assessment and certification, and 2.0 times higher than the average variable cost of assessment and average variable and fixed costs of certification. The gains to treated workseekers over just three and a half months easily exceed the cost of public certification and assessment.

The preceding calculation assumes that the treatment effect on weekly earnings does not vary through time from treatment to the endline. The public certification effect on earnings does not substantially vary with the time period from treatment to endline. But the treatment effects on recalled employment in the first and second months after treatment are not identical, suggesting a possible time trend (Table D.10). To account for this, we convert the weekly earnings effect into monthly terms and multiply this by the sum of the employment effect in the first month after treatment, the second month after treatment, and the week before the endline. This gives an average on earnings since treatment of USD 110.1, which also easily exceeds the cost of public certification and assessment.

# **C Labor Market Effects at the Extensive and Intensive Margins**

Treatment effects on labor market outcomes such as earnings and hours can occur at the extensive margin – due to treatment effects on employment – and at the intensive margin – due to treatment effects on job characteristics conditional on employment. This distinction is important, as intensive margin effects indicate that treatment is changing the type of jobs candidates secure. The intensive margin effects are not identified from regressions of labor market outcomes on treatment indicators for employed candidates, as the set of employed candidates may be selected based on treatment assignment.

We adapt a method from Attanasio et al. (2011) to decompose of labor market effects into extensive and intensive margins. We describe the decomposition here for earnings, but the same idea applies to any labor market outcome that is observed only for the employed. We use the term 44