The increase in income and wealth inequality since 1980 will have what effect on the U.S. economy? a.Decrease growth rates because spending power is concentrated in the hands of relatively few individuals with a low marginal propensity to consume b.Increase growth rates because spending power is concentrated in the hands of relatively few individuals who spend proportionally more than other income groups c.Unknown effects because the positive effects on spending by the wealthy could outweigh the negative effects on spending for the middle class d.Have no effect on growth rates because an economy's growth is determined technology and education