This is how your 2013 tax dollars were spent.

[AggregateDemand]

Looks like they've excluded Social Security and Medicare?

When discussing matters of budgetary economics, it is not preferable to follow the hypothetical mandates of the federal government. Social Security and Medicare should be included.

[AggregateDemand]

What is exactly is meant by government expenditure on "government"?

Administrative agencies. SEC, FTC, NLRB, FCC, EPA, etc

[AggregateDemand]

It's at the bottom of the picture.

Social Security is not included anywhere, and you can tell Medicare has been excluded because healthcare spending is about 40% higher than military spending.

[AggregateDemand]

Income tax revenue doesn't pay for SSI or Medicare.

Income tax is not supposed to pay for Medicare, but it does, particularly all of the senior citizen bills that are dumped onto Medicaid.

Anyway, you found the relevant information. This dollar only represents federal income tax spending.

[AggregateDemand]

Medicaid is for poor people who cannot pay for health insurance. It's only reasonable that that includes poor senior citizens who cannot pay premiums for Medicare Part B. Unless you think someone who has the misfortune of being both old and poor should just be SOL.

Seniors need two universal healthcare systems? This country has jumped the shark.

Medicare Part B isn't the problem. Long term care is the problem. People in the lower middle class have to be bankrupted by unexpected medical bills so grandma/grandpa can live long enough to let the LTC providers bilk the taxpayer.