The gap started closing after the laggard countries started respecting their citizens' property rights, removing price controls and trade restrictions, allowing individuals to engage in free enterprise and abandoning central planning. These policies have been called different names, but the common theme is this: the Government getting out of the way of the economy.
Oh right. There are setbacks but the overall trend is encouraging.
Fiat is the biggest setback. Its effects are blamed on capitalism and freedom. Bigger Government is justified by citing these effects, which ends up choking the economy and creating conflict. It's an insidious and vicious cycle. Bitcoin fixes this.