The International Monetary Fund has urged Asian economies to learn from Japan's experience and take action early to cope with rapidly-aging populations, warning that parts of the region risk "getting old before becoming rich."

According to an economic outlook report for the Asia-Pacific region published by the IMF on Tuesday, Asia has enjoyed substantial demographic dividends in the past decades, but the growing number of elderly is set to create a demographic "tax" on growth. The share of working-age population has begun decline in many Asian countries, posing a drag on growth.

The IMF report stated that, "Japan's experience highlights how demographic headwinds can adversely impact growth, inflation dynamics and the effectiveness of monetary policy". Japan faces both an aging and shrinking population, with its labor force shrinking by more than 7 percent in the past two decades. The high percentage of its citizens living on pensions may be behind the country’s excess savings and low investment, which are weighing on growth and blamed in part for keeping inflation below the Bank of Japan's 2 percent target. 

As for China, the IMF has classified it as a "post dividend" economy along with Hong Kong SAR, South Korea and Thailand. The report says, "These economies are projected to age rapidly and reach some of the highest old-age dependency ratios globally by 2050." 

As of the end of 2015, China's population aged 60 and above numbered at 222 million, accounting for 16.1 percent of the total population, according to figures released by the by National Bureau of Statistics.

2015 UN population projections saw the fertility rate gradually rise from 1.5 children per woman in 2010 to an estimated 1.7 by 2030 following China's move in 2013 to slowly relax the one-child policy.