When Baby Boomers die off, whites will be a minority. There’s nothing we can do at this point to fix it.
When that happens it’s going to be interesting times as the Chinese say.
The only thing which allows the underclass to have a high birth rate, is welfare. If there was no welfare, and an underclass girl was faced with the requirement to support her kids herself, through her own work, how many would she have?
Meanwhile, high taxes (to support the welfare state) makes having a large family (which would require the wife to have less of a presence in the work force) to be unaffordable.
Change these factors, and the respective birth rates will change.