I dont disagree, but Im also how you are tying this to my statement. What is changing over time in the US or Singapore? Is the opportunity cost getting higher?

I dont disagree, but Im also how you are tying this to my statement. What is changing over time in the US or Singapore? Is the opportunity cost getting higher? That could be an interesting idea. I suppose it is as salaries and material compensation increases, so does the opportunity cost. A homemaker has less opportunity cost than a female professional making 250k per year. It could be the case that the opportunity cost people are willing to pay for children is not perfectly elastic, and does not scale with income.