It seems to be using the CPI. The basket of goods & services the CPI is referencing is determined by the extensive Consumer Expenditure Survey, and reflects to a fair degree the actual spending habits of Americans.
Obviously, if you give more weight to housing, you're going to get different results. But it would distort the actual change in expenditure.
Obviously, if you give more weight to housing, you're going to get different results. But it would distort the actual change in expenditure.