From Levy and Rodrik:
What is striking is that this dualism has worsened during the period of Mexico’s liberalizing reforms. Research by one of us (Levy) shows that informal firms have absorbed a growing share of the economy’s resources. The cumulative growth of employment between 1998 and 2013 in the informal sector was a whopping 115%, compared to 6% in the formal economy. For capital, cumulative growth was 134% for the informal sector and 9% for the formal sector.
The short article is interesting throughout.