I agree that 50% population implosion seems incredibly high. However, I'm not sure where you got your 33% number for those 50+ years old. I went to the same website you pulled the data and downloaded the CSV file. Taking the sum of all the people 50+, the number is 662.5 billion (740 billion under 49 years). That's 47%. Using your birthrate, which seems quite optimistic since the birth rate was dropping before Covid, the population in 2050 would be (662.5-280) 382.5 million fewer people. Then take the 100 million the author claims as an overcount, and we're left with 482.5 million fewer Chinese. That's not 50% of the current population, more like 33%, but losing 1/3 of a population over 28 years does seem like a collapse. I'm sure the calculation is much more complex than this simple math though.
I agree that 50% population implosion seems incredibly high. However, I'm not sure where you got your 33% number for those 50+ years old. I went to the same website you pulled the data and downloaded the CSV file. Taking the sum of all the people 50+, the number is 662.5 billion (740 billion under 49 years). That's 47%. Using your birthrate, which seems quite optimistic since the birth rate was dropping before Covid, the population in 2050 would be (662.5-280) 382.5 million fewer people. Then take the 100 million the author claims as an overcount, and we're left with 482.5 million fewer Chinese. That's not 50% of the current population, more like 33%, but losing 1/3 of a population over 28 years does seem like a collapse. I'm sure the calculation is much more complex than this simple math though.