Who pays the mortgage interest?

Too many lines on this graph. Sorry. It had to be done:

Graph #1: Sorting out household interest cost

The lowest line is jiggy because it shows monthly data. The other lines show annual data and are smooth.

The jiggy line shows "personal interest payments" from Table 2.6. Personal Income and Its Disposition, Monthly. It's the lowest line on the graph. The green line runs close to it. I think these two are the same, except for two things:

1. the different frequencies (annual versus monthly) create some separation; and
2. the lines may be from different sources. Except they are NOT from different sources; both are from BEA.

But I still think these two lines should be the same. If not, then I don't understand what's going on here. As I understand it, then:

The green line shows interest paid by households on debt other than mortgage debt.

The purple line (above the green) shows interest paid by households on mortgage debt.

Green and purple together should add up to the total interest paid by households. They do.

The red line (with black dots) is really two lines. The red one shows total interest paid by households. The black-dot line shows the sum of the green and purple lines. The black-dot line matches the red line, so green and purple together do add up to the total interest paid by households.

So the graph can be simplified. Green and purple do add up to red. I correctly understand the component parts of total household interest cost. So we can forget about the red and black lines, and just consider the lower three lines.

The purple line, household mortgage interest cost, is definitely NOT counted in the jiggy "personal interest payments" line.

Mortgage interest is not counted as part of personal interest. This is probably because they figure the purchase of a home as business activity. This is something I never looked into but it has come up a few times. I remember Oilfield Trash telling me:

CPI views housing units as capital (or investment) goods and not as consumption items. Spending to purchase and improve houses and other housing units is investment and not consumption.

Clip from Table 2.6

So paying the mortgage interest isn't counted as use of personal income. Table 2.6 confirms it: "Personal interest payments" are part of the "Personal outlays" that are subtracted from "Disposable personal income". But "Mortgage interest payments" are not.

According to Table 2.6, subtracting "Personal outlays" from "Disposable personal income" leaves "Personal saving". 

Apparently, Mortgage interest payments are counted as part of Personal saving.

That doesn't sit right with me. Count the repayment of mortgage principal as saving, if you insist. But interest paid on the mortgage is income to somebody else. It is not part of my saving.

I need a cup of coffee.