单项选择题

C

Unemployment (失业) rose from 7.5% in June, 1996 to 7.8% in July, 1996, the highest rate since January of that year, the Labor Department reported. The main reason was a large increase—nearly 700,000 in the labor force, with a record 61.9% of the population over sixteen years of age working or actively looking for work. That growth was caused mainly by an increase in the number of women in the labor force, an increase partly because of a continuation of long-term and economic trends (经济趋势)and partly a reflection of pressure on families to increase their incomes.

Why did unemployment increase during the period discussed in the passage