I don't know, but the number would be non-zero. People try to thwart the law all the time in all sorts of circumstances even given the possible consequences if caught. I mean if people really universally thought of the consequences first and that acted as a deterrent, we wouldn't have crime.
The number doesn't have to be zero.
Naturally there's always going to be some porosity at the border and in the labor market.
The goal is the creation of a filtration system that captures the turds, the toilet paper, the toy soldier little Johnny flushed, the bacteria and most of the viruses so the pool can once again be considered fit for human use. There's going to be the stray virus, the occasional ameoba that gets through, but as it stands right now, the nation is drinking pure sewage and the nation's immune system, the Border Patrol and the ICE cannot fight the magnitude of the infection.
When sane policies, such as the impoverishment of employers caught knowingly hiring illegals, are in place and the invaders who don't wish to go to jail self-deport, the remainder will be the real criminal aliens law enforcement is best equipped to catch and prosecute.
I certainl support the idea that the funds collected from the impoverishment of the employers of illegal should be made available to give invaders who voluntarily turn themselves in a no-charge ride to the border or their nation of origin, after they're finger printed, DNA'd, photographed, and informed that re-entry illegally is a felony (which it isn't right now, but should be).
National sovereignity is not something that should be thrown away for temporary political expediency.
The Democrats and Republicans who have allowed this invasion to proceed unabated for nearly three decades have allowed the importation of a potential hosile army inside our borders commingled with citizens, and in the event that this army is activated, it's not going to matter to the political leaders south of the border who commands them what our fifty column politicians did to help them.