Offer $4,000 to anyone 18 and older to become sterilized.
People who can't afford kids keep shitting out kids. Then these families rely on government programs for assistance, placing a greater burden on taxpayers. A fee of $4k may sound like a lot to offer someone up front, but in the long run it's going to save this country billions. Additionally, this fee is going to appeal to the demographic we don't want fucking in the first place. Inattentive, irresponsible parents are the bain of every human's existence. Their children grow up in the same regard, and the cycle continues.
What is the harm in offering people money to not do what they shouldn't be doing in the first place?