There are no such things as saturation points and surpluses of unskilled labor. The amount of work out there to be done (i.e. the distance between the world we live in and a perfect one) is infinite.
I'm open borders and such, but I'd be very careful about saying that we can never have a surplus of labor.
If the government gave subsidies to have children you could theoretically reach a point where the population increase outpaces the amount of capital available and living standards decrease. I am extremely doubtful that this will occur in real life and I can only think of three occasions where governments have tried this: (1) modern Russia, (2) modern Singapore, and (3) NAZI Germany. In all three cases the subsidies were all too low to significantly change birth rates.
Could we have a general surplus of labor? Theoretically yes. It is extremely unlikely that this will ever occur and the subsidies involved would be astronomical even relative to today's welfare state.
What is more likely, and does exist, is overpopulation in specific regions. Mind you, this is 'overpopulation' in the same sense that California's central valley is 'overpopulated' with more fruit and foodstuff than the locals can eat. The obvious solution to this problem of regional overpopulation is to allow labor to freely move towards where it is more it is more productive.
Too many people here are not acknowledging the current state of America, regarding the welfare government. Until this is changed, illegal immigration is DEVASTATING the US economy. And before someone writes dissertation trying to explain Austrian economics, save your time. I already know and agree, but I am also looking at the now and real, and not what I wish. And if you need proof, a great example is the Dominican Republic. With it's smaller population, 10 million illegal immigrants from Haiti have destroyed their nation.
There is a net negative fiscal cost that can be attributed to young immigrants (both legal and illegal) and natives newcomers (i.e. babies). I am speaking about the welfare given to kids in the form of free or reduce healthcare, schooling, free meals at said schools etc etc. We definitely need to reform the system on this end to make it more efficient.
Adult migrants (legal or illegal) however don't have a negative fiscal cost. Most of them are in their working prime and don't demand government services themselves.
Deporting the latter wouldn't do much to help us fiscally. Deporting migrants in their prime age would actually harm us fiscally since they are net taxpayers. Deporting young migrants (legal or illegal) and aborting every baby-to-be in the United States would be more effective if your goal is to preserve the fiscal integrity of the United States government. This is of course lunacy and not something I could support. I should hope no one here could such things either.
Let's reform our welfare system instead, okay? Are we still going to incur losses? Yes. Even if we introduce a nationwide voucher system or reform welfare to be needs based we will still need wealth distribution and all the negative aspects associated. I'm okay with this. As far as taxes go, I'm okay when it comes to supporting schools and welfare for the young though. In a stateless world I would not mind voluntarily donating to these causes.