China's assessed contribution to the United Nations is likely to outstrip Japan's by more than 2 percentage points between 2019 and 2021, during which China's share is expected to reach 10.8 percent of the total, nearly 3 percentage points more than that in the 2016-18 period. That will make China, which contributes more than 10 percent of the UN peacekeeping budget, the second-largest contributor to UN funds.

The probable decline in Japan's contribution may hamper the country's pursuit of a permanent seat in the UN Security Council. But the changes are not unexpected because, according to the principle of "capability to pay" that governs the scale of assessment, China has become a more capable contributor.

Despite its slow growth, the Chinese economy is largely healthy and now accounts for 14.8 percent of the global GDP. In contrast, the much-touted "Abenomics" has added little impetus to the Japanese economy, hindering the country's capability to contribute more to the UN budget.