Its a nice thought, but the math doesn't work. 15% is roughly 1 in 6, which is to say that if each person maintained one hen and two broilers, they'd be kept in chicken. I don't like eggs, and use more than 200 to 250 eggs a year. and I certainly eat more than two broilers a year, to say nothing of the chicks you would have to hatch to replace aging layers and replace culled broilers.
Tyson processes 45 million chickens a week, there are about 300 million of us in the US. If they were the only chicken producer (obviously, they aren't here in the US), that's 8 broilers per person per year. US residents actually eat almost 100# of chicken per year, or roughly 2# of chicken per week, call it two broilers per month.
Thats either more owners or larger flock sizes, or both. How large depends on how eggs are beign ijncubated, hatch rates, mortality, rate of lay. My guess is that the numbers would be more like 15% of the pop maintaing a flock of 24 layers 18 if they are prime production birds) and 36 broilers, with incubation, 90% viability, and a decent rate of lay from the broilers.
So, on the right track, but needs a recheck on the math.