On the empirical evidence of competing theories regarding informality

Yesterday we talked about the theories that explain informality. The point under discussion was whether labor markets where segmented or not segmented. Despite the importance of the topic, few empirical studies have analyzed the issue. There are some papers for Mexico. Basically most of them argue that labor markets, at least the urban ones, are not segmented. Different findings support the idea:
There is important rotation of workers between the formal and the informal sector
Informality also grows in periods of economic expansion
It is observed that wages in the formal sector reflect that the workers have other opportunities outside the formal sector, i.e., in the informal one
Affiliation to social security institutions have decreased after the introduction of health programs universally provided and financed by general taxation
Some surveys indicate the indeed some persons recognize that they prefer the informal sector given the characteristics of the job, the most important one, being flexibility
Whether these findings can be considered a conclusion, it is too early to know. More research is needed for the case of Mexico and for all other countries that have an important informal labor market.