While I don't disagree, it's hard to explain, and even harder to prove, in strictly econometric terms. I think it has something to do with the people who receive the money actually working for it, and being of a high enough socioeconomic level (except the grunts of course) that they spend more of their income on big ticket items and so called "luxury goods", which seem to have a higher multiplier factor than the bare necessities which most (but not all of course) welfare and other social spending dollars go to.
I was thinking more of physical security and a stable form of government as intangibles that are a huge benefit to the economy. For example, when the latest latin dictator starts talking about nationalizing things, many wealthy south Americans move their assets to Miami. This helps the wealthy south Americans, who don't lose their money to the thug of the month, and helps Miami's economy, also.
One of the missions of the Navy is to keep open the sea lines of communication, a side benefit of which is the protection of civilian shipping. That's an intangible that allows businesses to operate confidently. Very hard to put a price tag on.
I think too many on this board have a knee jerk "all government is bad" mentality. I take a back seat to no one in wanting a smaller, cheaper government. But the founding fathers put "provide for the common defense" in the Preamble for a reason. If you can't defend it, you're not going to keep it very long.