Not really a very good survey since it should separate out the very different groups in the population by race and gender and income level etc. Nevertheless, for what it is worth, here are the excuses people have for not wanting more kids.
Kids are great. Get some.
Table: “Why Young Adult Americans Are Having less Children: These Are The Reasons People Expected to Have Fewer Children Than They Considered Ideal”, in New York Times, July 6, 2018. p. B5.
(One major concern that does not directly appear is high levels of student loan debt.)
Child care too expensive: 64%.
Want more time with children I have: 54%.
Worried about the economy: 49%.
Can’t afford more children: 44%.
Waited because of financial instability: 43%.
Want more leisure time: 42%.
Not enough paid family leave: 39%.
No paid family leave: 38%.
Worried about global instability: 37%.
Struggle with work-life balance: 36%.
Worried about domestic politics: 36%.
Met a partner too late: 34%.
Worried about climate change: 33%.
Responsible for other family care: 29%.
Worried about population growth: 27%.
Prioritized my education and career: 23%.
Split from my partner: 22%.
Partner doesn’t want children: 19%.
Don’t think I’m a good parent: 13%.
Source: Morning Consult survey of 1868 men and women aged 20-46.