Average household income is simply average per capita income multiplied by average household size. (This would not be true for median, but I wanted to illustrat

Average household income is simply average per capita income multiplied by average household size. (This would not be true for median, but I wanted to illustrate how simple it is). Household size has been decreasing over the last 50 years (less people per family unit), and household income is therefore growing more slowly than per capita income. It's still growing though. All this is available from FRED data.