What is the importance of the Sonagachi Project in the nonfiction book, Half the Sky?

Kristof and DuWunn Sonagachi, India, is a red-light district in Kolkata. It had been the locale for concubines in the eighteenth and nineteenth centuries. In current times there are hundreds of brothels in the region that contain more than 6,000 prostitutes.

Due to great concern that it would be a hotbed of the AIDS virus in the 90s, the Sonagachi Project was launched with the support of the World Health Organization (WHO). The project called for unionization of sex workers to encourage safe practices including condom use to reduce the spread of the HIV virus.