What is the theme in London Labour and the London Poor by Henry Mayhew?

The book relies heavily on stereotypes rather than empirical evidence and data. According to Mayhew, certain nationalities and sexes have an affinity for specific occupations, such as Irish fruit vendors, French female singers, Italian organ players, Jewish clothing salesmen, and Dutch girls who sell brooms. It does not occur to Mayhew that these occupations may be the result of limited opportunities. Instead, he sees them as a natural outgrowth of innate characteristics, much as an insect with wings has a predisposition to fly.