"Credible" critics (as in least noncredible) i.e. YiFuxian undercount in <10% range, which comports with bureaucratic incentive to overcount before digitization when head count hard to track.

>perhaps by 100's of millions

More than 10%, i.e. PRC actually only 800m-1000m (20-30% undercount) is when claims become statistically retarded. There's proxy indicators like PRC ag imports, especially animal feed (soybeans), if they were 100s of millions short then per capita caloric consumption reach biologically impossible levels (like 200 grams of protein / 5000 calories per capita) meanwhile key policy CCP (Xi personally) hammers is food security / wastage. This when demographic skepticism becomes unhinged.

TBH PRC over reporting pop, UNDER reporting GDP is sensible. PRC entire history has been trying to underreport GDP (specifically per capita gdp) using accounting methods to stay under high income status for development perks, literally since initial IMF negotiations to set PRC per capita baseline, PRC insisted on something like 50% lower than what IMF calculated. Of course the anti PRC faction won't accept the logical out come is that PRC that is much richer it claims, with less people than it claims, i.e. PRC per capita much higher than it claims only makes PRC system look stronger. Then factor in demographic income disparity (i.e. tertiary educated newer gen make multiples more) and realize as PRC demo phases out undereducated/unproductive elders in next few generations and PRC per capita is statistically locked into doubling/tripling. Then factor in PPP / potential future FX moves, i.e. PRC appreciating rmb is another multiplier on PRC per capita. Not many "honest" economist talks about how PRC is actually incentivized to look statistically weak (somehow people forgot about hide/bide when it comes to economy), because muh authoritarians like to look strong, leading to plenty of PRC doomer economists who keep being wrong.