In 2017, the top 5% of households saw average income rise to 8.7% higher than pre-recession levels. But among the bottom fifth of the population, average income grew--but still remained 2.7% below pre-recession figures. And that's a problem for fast food chains. According to Business Insider, Wendy's CEO says that lower-income Americans are "not participating in the real wage growth" to the extent that the rest of the United States is.