<mark>Despite these advantages, Internet surveys conducted with RDIT could be biased because of nonprobability-based sampling.</mark><sup>5</sup> <mark>To better understand these biases, we take two approaches to assess the quality of internet survey estimates. The first approach compares time-invariant measures, particularly demographic variables, calculated from the online surveys to nationally representative surveys collected prior to the crisis, contained in the World Bank’s Global Monitoring Database (GMD). The results indicate that online surveys represent a substantially different demographic group compared to the national picture, overrepresenting male, younger, and more educated members of the country’s population. Therefore, using the raw online survey results to track labor market indicators would be misleading.</mark> <mark>As a first quality check, we attempt to address the bias described above using a propensity score adjustment, based on the estimated probability of participation in the Internet survey. In particular, we estimate a logit model of selection into the online survey, as opposed to the GMD survey, in each country. The model is used to construct weights equal to the inverse of the predicted propensity scores. The results show that, for variables included in the propensity score calculation, the reweighting process produces a smaller deviation of the means of the internet survey from the GMD survey. The deviations between variables excluded from the propensity score model, however, remain relatively high. For example, the deviation for model variables was 32.0 percent in Brazil, but 56.8 percent for the non-model variables. In Indonesia, while the deviation for model variables was 15.3 percent, the deviation was 582.0 percent for non-model variables. This result highlights that it is problematic in this context to assume that selection bias becomes ignorable after conditioning on demographic characteristics such as age, gender, and education.</mark> <mark>The second quality check compares reweighted estimates of labor market indicators from the internet survey with other nationally representative data available in the same time period. This comparative data came from PNAD in Brazil, labor force surveys from Sri Lanka, Türkiye, and Indonesia, and the Continuous Household Survey from Kenya. Looking at the employment-topopulation ratio, the reweighted online survey captures the national picture reasonably well in Türkiye, but considerably overestimates the employment-to-population ratio in the other countries. On average, the internet surveys give employment-to-population ratios that are 30 percent above the rates from the benchmark data. We also examined the relationship between internet coverage in a country and how well the online survey in that country captures the employment-to-population ratio accurately. Notably, Türkiye has the lowest deviation and the highest Internet coverage, but other than that there is no systematic relationship between Internet coverage and prediction accuracy.</mark> <mark>We also examine two other labor outcomes, namely, the formal employment-to-total employment ratio, and the self-employment-to-total employment ratio. The sample size for these indicators is much smaller than that for employment as these questions were only administered for a subsample of those employed.</mark><sup>6</sup> <mark>The performance of the online survey in tracking formality</mark>

> 5 Besides non-probability-based sampling, another issue with standard Internet surveys is the potential duplication of responses. The same respondent can potentially answer the survey several times.  However, the RDIT can identify the device of the survey respondent using a combination of the respondent’s IP address, device details such as device type, internet browser, operating system, and other device details, and thus prevent the same device owner from participating in the survey multiple times. While the same person could potentially take the survey from multiple devices, the opportunity cost of time could prevent them from doing so.

> 6 The employment related questions were administered to all those taking up the survey. We define as employed those who mention that they were “employed at work” and “employed but not at work”.  The formality and self-employment related questions were administered only to those who are “employed at work”.

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