How much tax to levy? There are no easy answers

"The weakness in the overall economy weighed on revenue growth, which for the first time in years underperformed GDP growth and caused the tax burden ratio to decline," said Hu Yijian, a tax professor at Shanghai University of Finance and Economics.

China's fiscal revenue growth in 2015 slowed to 5.8 percent, its slowest pace since 1987, when GDP grew 6.9 percent. Land sales tumbled 21.4 percent from a year earlier because of a downturn in the property market.

But 2015 was a departure from the past decade, during which fiscal revenues expanded much faster than the overall economy.

Although China cut taxes in 2015, contributing to a lower revenue-to-GDP ratio, the country's tax burden last year, measured in the broadest terms, was still higher than many others, even some developed countries. Members of the OECD had an average ratio of 34.4 percent.

"China's government is large and should not increase," said Lin Shuanglin, director of the China Center for Public Finance at Peking University. He said the ratio might have reached its peak.

However, "it is not a matter of the lower the ratio, the better", he said. "Many countries, such as Indonesia and Thailand, have very small governments and macro tax burdens around 20 percent, and are struggling for needed public infrastructure.

"What they need is to raise their tax revenues," he said.