[cheriot]

That's a reflection of a growing economy. Real incomes are higher so people have more to spend.

Edit: add data

Real personal income https://fred.stlouisfed.org/series/RPI

Real GDP https://fred.stlouisfed.org/series/GDPC1/

[cheriot]

I think I'm getting the unit right on this graph. Food at home as a percentage of disposable income: https://fred.stlouisfed.org/graph/?g=1aWLA