BEIJING—Fresh doubts emerged over the reliability of Chinese statistics on Wednesday after officials said the economy grew 6.7%—for the third consecutive quarter.

It was the first time since Beijing started releasing quarterly figures in 1992 that it had achieved such a feat of consistency.

Economists say it is rare for a fast-growing economy to clock the same growth quarter after quarter. In China, it happens because Beijing sets a hard economic target—6.5% to 7% this year—then does what it takes to reach this level, whether through fiscal stimulus, arm twisting of state companies or creative accounting, these people say.

The International Monetary Fund and numerous economists have urged Beijing to scrap that system, saying it leads to excessive fiscal stimulus that fuels manufacturing overcapacity and debt.

“It’s quite implausible that growth would be 6.7% for three straight quarters,” said Julian Evans-Pritchard, an economist with Capital Economics Pte. “They’re obviously smoothing the data quite a bit” he said, adding: “Even by Chinese standards, this is a new level of stability.”