This was a very interesting (if extremely short) article in The Economist about military spending per capita:
Israel spends most on defense relative to its population, shelling out over $2,300 a person, over $300 more than America. Small and rich countries, and notably Gulf states, feature prominently by this measure. Saudi Arabia ranks ninth in absolute spending, but sixth by population. China has increased spending by 10% to $85 billion to become the world's second largest spender. But it is still dwarfed by America, whose outlay of $607 billion is higher than that of the next 14 biggest spenders combined.
That Singapore comes in at #4 is a little surprising (I would have expected it to be a little lower down on the list), but I'm not surprised that it and some of the other small countries (Bahrain, Brunei, Kuwait, Oman, and Saudi Arabia) are there: all have valuable assets (mostly oil, and a very modern economy in Singapore) that would make nice war prizes for neighboring countries (witness Iraq's attempted grab of Kuwait back in 1990). Israel's there for the obvious reason (let's not forget that much of that military spending goes for the occupation and oppression of the West Bank and Gaza). The bigger surprise for me is the listing of some of the European countries: Denmark, Greece, Norway and the Netherlands. Is it because the cost of participating in NATO is that high or because owning the best military hardware is that expensive?