????Take Europe's case. Since the 1980s, the region has grown slower than the United States. Unemployment in Europe ranged 8% to 10 %, while U.S. unemployment ran around 4%.

????"They have not created many jobs -- why not? Because they're not spending in places to create jobs," Meltzer said in an interview with Fortune in February about how the Obama administration got Keynes wrong. Government spending in Europe has focused more education, health care and other expenses more helpful with stimulating consumption.

????No doubt Keynes was brilliant, and he'll always be considered a legend. To many respected economists and policymakers, his philosophies on how the economy should work were accurate. But in many ways, it's worth wondering if the growing complexity of the global financial system may have caught up with the answers he developed decades ago.

????The marketplace is increasingly influenced by people's expectations of the future, including the scale of debt -- something Keynes didn't take into account. And as the marketplace becomes more complex, it also becomes more challenging to predict.

????"Keynes was too smart to make a mistake -- the problem is we live in a different environment," said Nassim Taleb, author of The Black Swan, which looks at the impacts of improbable events. Taleb added that with debt levels as high and problematic as they are in parts of Europe and the United States, accurate forecasting on indicators such as unemployment rates become more crucial.

????Too often, forecasts have been wrong. Which makes Keynesian economics harder to follow in today's modern economy.