Average Income over Lifetime

The Wall Street Journal has the following graph showing average income over he course of a lifetime. The big point of the article and the graph is how income plateaus at age forty. This reality runs counter to how most people see their income growth over heir lifetimes (what would this mean for the idea of the "lifetime income hypothesis"?) The bigger point is that people's expectations of quickly rising incomes in their fifties might result in people underfunding their retirement plans.