This 1988 Government Accounting Office report (60 pages) to Senator Charles Schumer was authored covering the period during the Reagan presidency.
http://archive.gao.gov/d17t6/136973.pdf
(emphasis added)
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[page 2]
The restaurant, apparel manufacturing, and meat-processing industries
were those most often cited as having serious problems with multiple
labor law violators, and Hispanics and Asians were said to be the ethnic
groups most heavily represented among workers in these establishments.
About half of the federal officials gave some estimate of either
the number of businesses or workers in sweatshops, and these estimates
suggest that many workers may be underpaid and working in unsafe or
unhealthy conditions. For example, one respondent estimated that half
of the approximately 5,000 restaurants in Chicago, with about 25,000
workers, were multiple labor law violators. Another estimated that a
quarter of the approximately 100 apparel firms in New Orleans are violating
multiple labor laws with about 5,000 workers.
Overall, many
thought the problem in apparel manufacturing and restaurants had not
improved or had become more severe during the last decade.
Several factors cited as reasons for multiple labor law violations were
similar to those that existed in the 19th century--a
large immigrant
work force and
low profit margins in labor-intensive industries. But
some federal and state officials also attributed the presence of sweatshops
to such factors as
too few inspectors and inadequate penalties.
//