Comparing against the fertility rate is completely meaningless. The fertility rate includes all the people who have zero children; and it also counts the children people have over their <i>entire</i> lifetime.
If you're a HN parent please fill out the survey so I can get some better data :) <a href="https://animikii.wufoo.com/forms/hacker-news-little-startups/" rel="nofollow">https://animikii.wufoo.com/forms/hacker-news-little-startups...</a>