Final answer:
The increase in income inequality is not attributed to the rise in two-wage families; rather, factors like demographic trends, the decline of manufacturing, and global competition are responsible, alongside the widening wage distribution favoring high-skilled workers due to winner-take-all labor markets.
Step-by-step explanation:
The contemporary increase in income inequality may be attributed to several factors, but an increase in the number of two-wage families is not one of them. Factors contributing to this trend include demographic trends that result in a workforce with fewer older, more experienced workers, the relative decline of the manufacturing sector and the resultant rise in service-oriented jobs which often pay less, and global competition that puts downward pressure on wages. Conversely, two-wage families actually help to mitigate inequality by increasing household incomes.
Another significant factor contributing to growing inequality is a shift in the distribution of wages, which has begun favoring high-skilled labor over low-skilled labor since the 1970s. This gap has widened due to winner-take-all labor markets, propelled by technological changes that have heightened global demand for talented individuals ('stars'), but this is not mainly due to educational differences. Such a market inflates the salaries of top earners in a disproportionate way, compared to their overall productivity or education level.