Generally speaking, you would want to take a random sample of employees, verify that the information they self-reported was correct, and perform a regression an

Generally speaking, you would want to take a random sample of employees, verify that the information they self-reported was correct, and perform a regression analysis of response rate vs. other characteristics (age, seniority, gender, salary, ethnicity, etc.). In this particular context, the biggest threats to data integrity are probably: 1. People lie, and men probably lie about their salaries more than women, 2. Willingness to divulge salary is highly culture-dependent, and in societies where salary is seen as a sign of social success, can be highly salary-dependent (and probably more so for men than for women). If you're interested in learning more I suggest looking for information about how national census data is processed; they have lots of experience dealing with these sorts of issues (albeit with different factors influencing response rates and data reliability).