Thesis: In the first part it analyses the effect of employment protection legislation on worker flows, i.e. the rate of worker reallocation, in OECD countries. Findings suggest that the more restrictive the regulation, the smaller is the rate of within-industry job-to-job transitions, in particular towards permanent jobs. By contrast, it finds no significant effect as regards separations involving an industry change or leading to non-employment. The extent of reinstatement in the case of unfair dismissal appears to be the most important regulatory determinant.The second part revisits the debate on minimum wages in Europe bringing new evidence on systems without a statutory minimum wage and comparing them with countries with a statutory one. Results show that systems with bargained sectoral-level minima are associated with higher Kaitz indices than systems with statutory floors, but also with more individuals actually paid below prevailing minima. Higher collective bargaining coverage can to some extent reduce this trade-off between high wage floors and non-compliance or non-coverage. The third part brings some evidence on the effect of diversity on firm productivity and wages in Belgium and France. Findings show that educational diversity is beneficial for firm productivity and wages while age diversity is harmful. Gender diversity is found to generate significant gains in high-tech/knowledge-intensive sectors or in family firms, while a negative effect is found in more traditional industries or in non-family firms.