Which method? To give you an idea, even "Certified Humane" hatcheries grind the male chicks alive. Definitely standard when it comes to factory farms. I would say the grinding method is most common based on the hundreds of undercover investigations I've seen, but gassing in plastic bags is another common method. And apparently electrocution is another method but I've actually never seen an undercover investigation showing that except with adult hens.
This is a map of factory farms in the country:
That's where pretty much all animal products come from, then combine that with the smaller percentage of "humane" farms, all of which (except maybe some extremely fucking rare one somewhere that probably doesn't produce more than to feed a couple families tops) kill the male chicks right after they hatch.
Pretty damn rampant.