Philip Ewing, in an article on Politico Pro about the vice presidential debate, asserts that comments about defense spending by Representative Paul Ryan (R–WI) signal that Governor Mitt Romney could abandon his pledge to maintain the defense budget at 4 percent of gross domestic product (GDP).

Ewing is jumping to conclusions based on differing definitions of what is either a cut or an increase to the defense budget. Ryan asserts that Romney’s defense budget proposal means that a future Romney Administration would just not impose the reductions on the defense budget proposed by the Obama Administration. Vice President Biden asserts that the 4 percent pledge means a $2 trillion increase in the defense budget.

In short, Ryan is right and Biden is wrong. The confusion stems from the process of converting the 4 percent allocation for defense into dollars and then comparing the dollar figures to a baseline that nobody can agree how to define. Biden wants everybody to accept the premise that the Obama Administration gets to define the baseline in any way it wants under the dollar conversion. Accordingly, using the dollar conversion makes describing the true state of affairs needlessly complicated.

The clearest and most direct way to cut through this complication is to compare the Obama Administration’s proposed defense budget (setting aside the automatic spending cuts that may be applied starting next year under the Budget Control Act) and Romney’s proposal as shares of GDP and forgo the dollar conversion.

According to data provided earlier this year by the Office of Management Budget, the defense budget is estimated to have consumed 4.7 percent of GDP in fiscal year (FY) 2011. By definition, the Romney proposal would let the defense budget fall to 4 percent of GDP and keep it at this level.

According to the same data, the Obama Administration’s proposal would reduce the defense budget to 2.6 percent of GDP by FY 2022. This is why Ryan is right when he talks about the Romney defense budget proposal as simply not applying the reductions that the Obama Administration has already proposed.