using a method or in a time period we do not measure. These changes in search behavior may generate higher employment and earnings, even if firms face no information frictions and do not respond to certificates. In the next section, we address this possibility by discussing an experiment that directly manipulates firms’ information, without any scope for changes in workseeker behavior.

# **4.3 Firms Face Information Frictions**

In this section, we show that revealing information only to firms changes their responses to job applications, without allowing any potentially mediating behavior by workseekers. This is consistent with firms facing information frictions and the employment and earnings effects of certification being partly explained by firm-side information frictions.

We describe results from an audit-style study, with more details on the experiment in Appendix E. We invite a random sample of assessed candidates to send us a resume that we will forward to prospective employers on their behalf. We create a list of job vacancies by scraping online job advertisements. We eliminate scam vacancies and vacancies that require work experience or university education, where many candidates in our sample would be ineligible. We send resumes from 4 randomly chosen candidates to each vacancy, each from a different email address. We generate two outcome variables based on the email responses from firms. ‘Interview invitations’ are invitations to interview with the firm. ‘Any responses’ are similar to ‘callbacks’ in other audit studies and include interview invitations and requests to provide more information by email or by visiting the firm in person.

We randomize each vacancy to receive either 1 or 3 resumes with public certificates attached. We also randomize which of the resumes are chosen to receive public certificates. This design motivates the estimating equation where _Yrv_ is the response to resume _r_ sent to vacancy _v_ , Certificate _rv_ is an indicator equal to one if the application includes a public certificate, HighIntensity _v_ is an indicator equal to one if the vacancy receives 3 applications with certificates rather than 1, **V** _v_ is a vector of vacancy fixed effects that subsumes the main effect of HighIntensity _v_ , **X** _v_ is a vector of prespecified resume covariates, and **E** _rv_ is a vector of fixed effects for the email addresses used to submit the applications. We cluster standard errors by resume and vacancy.<sup>20</sup> _β_ 1, the effect of using a public certificate when other applications do not, is positive. Applications with a public certificate are 1.6 percentage points more likely to get any response and 1 percentage point more likely to get an interview invitation (Table 4, columns 2 and 4). These are substantial

> 20Like most audit studies, we submit the same resume to multiple vacancies. Each resume includes a certificate for half of these vacancies. Audit studies generally cluster standard errors by resume (Neumark, 2018). Abadie et al. (2017) recommend clustering by the unit at which treatment is assigned. We therefore cluster by both vacancy and resume. Results are very similar when clustering only by vacancy or only by resume.

23