I think there is a mistake in the annual size of the pregnant woman market. To prove my point, there is 15 million woman pregnant at given time in China. This is correct. Assuming lineral growth there is 1.(6) new pregnencies each month (15m/9). So annually there is 12 * 1.(6) new pregnancies that is equal 20 million of kids on average each year. So the market size should be 20 million, not 15 million. Sure, there are some woman that got pregnant at the end of the year, but there are also some that got pregnant at the end of previous year, so on average the annual market size in terms of # of woman is 20 million. We also have an average expenditures per customer per year. So the market size in value is $150 * 20m * 10% = $300 mln
Other way round I initially calculated the number of children each year by:
750m (# of woman) * 2 (number of children per life) / 75 (average life expectancy)
This gives you also 20 million children per year and I think this is also a good way to calculate th market size.
Please let me know if you agree or am I wrong?