It is obvious from the passage that ....... .

Whatever their occupation, practically the entire population of Detroit depends indirectly on the
automobile industry. No other major American city depends so much on a single industry for its
livelihood. When the automobile industry suffers, the entire population suffers. And since people
tend to postpone car purchases during recessions, the whole industry can go into a tail-spin
during hard times. This is why Detroit had an unemployment rate of more than 15 percent
during the recessions of the early 1980s and early 1990s. But when times are good, automobile
workers command salaries that are higher than wages in manufacturing in the rest of the country.
One of the reasons wages are higher is that Detroit has long been a centre of organised labour,
and the unions have fought hard to keep wages high.