The issue
NATO countries are supposed to spend 2% of their GDP on defense.
The facts
The NATO agreement to have member countries fund their own military with 2% of GDP is in place so that each country can defend itself without relying too much on other members — but of 28 NATO members, only five meet this requirement.
Romania pledged an increase in defense spending that is expected to bring it above 2%. Poland, which already meets the 2% line, pledged in October to increase the country's defense spending to at least 2.5% of GDP. NATO expects Latvia to meet the threshold by next year. Denmark expects to increase its spending to 1.3% of its GDP by 2023. Hungary expects to meet the 2% threshold by 2026. Canada is set to increase its defense budget to 1.4% by 2025. Slovenia said this year it would start increasing defense spending for the first time since 2010.
Why it matters
Donald Trump has criticized NATO as being "obsolete," though since becoming president he's softened his tone. Defense Secretary Mattis on his first trip to Europe warned NATO countries to meet their defense spending goals or the U.S. might "moderate its commitment" to the alliance.