According to the SIPRI Yearbook 2009, global military expenditure has risen by 45% over the past decade to $1.46tn. Chapter 5 in the Yearbook deals specifically with this issue. That's 1.46 trillion US dollars. I've created a little chart to better illustrate this:

The USA spent more than 7 times the amount of money (607 billion US dollars) on weaponry than the runner-up, China, did. I know the reasons for buying guns are not founded per capita, but the population of China is 326.9% larger than that of the USA. Anyway, no matter what you use to try and justify the purchase of arms, all of this is just insane.

From The Guardian:

Though the US accounts for more than half the total increase, China and Russia nearly tripled their military expenditure over the decade, with China now second only to the US in the military expenditure league table.

Here's to global peace! I think Chapter 5 from the Yearbook clearly high-lights the problems that the USA have, due to their arms-race and invasion of countries ((Quoted from this page.)):

During the eight-year presidency of George W. Bush, US military expenditure increased to the highest level in real terms since World War II, mostly due to the wars in Afghanistan and Iraq. This increase has contributed to soaring budget deficits. The conflicts in Afghanistan and Iraq have been funded primarily through emergency supplemental appropriations outside the regular budgetary process and have been financed through borrowing. The use of supplemental appropriations has raised concerns about transparency and congressional oversight. These conflicts will continue to require major budgetary resources in the near future, even supposing early withdrawal of US troops from Iraq.

Below is the data that I culled from the yearbook and pushed into a Google Spreadsheet to make the chart above: