What percentage of gross domestic product should a country be spending on its defense?

That question has continued to be at the center of debates on defense, with NATO allies recently committing to increase the target from 2% to 5%. The White House has since stated that 5% should be the standard for all of America’s allies. Voices around the globe are arguing the pros and cons of such a target.

In truth, the “percentage of GDP” approach is a political one, not a practical one. The actual debate is far more complex and includes alliance management issues that have existed for as long as there have been military alliances.