Final answer:
Despite the dramatic increase in female labor force participation since the 1970s, which nearly doubled the workforce, there has been no long-term significant trend in unemployment rates. The U.S. economy has adapted to demographic changes, globalization, and technological advancements maintaining employment levels.
Step-by-step explanation:
Changes in the American labor force since the 1970s have been marked by several significant trends, but not all the observations hold true. Notably, there has been no significant long-term upward or downward trend in unemployment rates. This stability in unemployment is remarkable given the substantial demographic changes in the workforce, primarily due to the increase in the number of women in the labor market. In 1900, women constituted 18% of the paid workforce, but by 2017, they made up nearly half. Despite this dramatic rise in labor force participation, alongside other influential factors such as globalization and technological innovation, the U.S. economy has managed to absorb the added number of workers without a corresponding long-term rise or fall in unemployment levels.
When women began joining the labor force in large numbers, starting in the 1970s, if wages were assumed to be 'sticky' in a downward direction and labor supply increased, one might expect wages to remain the same or possibly decrease and unemployment to potentially rise in the short term due to a surplus of labor. However, the data reveals that employment has continued to burgeon, and wages, over time, have generally followed an upward trend, adjusting to the market pressures and productivity gains, although not uniformly across all sectors.