Maximum, that is.
1 child policy from 1979 to 2015.
2 child policy from 2015 to 2021.
3 child policy since 2021.
The announcement came after the release of the results of the Seventh National Population Census, which showed that the number of births in mainland China in 2020 was only 12 million, the lowest number of births since 1960, and the further aging of the population, against which the policy was born.[5] This was the slowest population growth rate China experienced.[6]
Although the CCP government had high expectations for the new policy,[16] in a 2021 online poll conducted by the state media Xinhua on its Weibo account, using the hashtag #AreYouReady for the new three-child policy, about 29,000 out of 31,000 respondents stated they would “never consider it.”[15]
A gradual decline in population is a good thing, so they probably don’t want to overshoot too much. Also maybe the minorities pushed for keeping some restrictions.
From what I understand, the one child policy tanked their birthrate so much that the country is expected to never recover. Current economies are basically dependent on a growing population to support the elderly and retired members of the population. Countries can somewhat get by through immigration to prop up a low birthrate, but that can only take you so far.
This applies only when labour is in short supply. Japan and Germany have heavily automated their industry for this reason, and China seems to be on this track.
Apart from the labour shortage, a gradually declining population is a good thing. The earth can only give us so many resources, and unless we reduce our numbers - particularly among the rich - we are headed towards extinction.