I've only got 4 hens (born last April) but 3 are Leghorns so I think they do exceptionally well. I do not add artificial light to stimulate production (although they have a red heat lamp for the first time this winter starting tonight)
I would say on average that production is down at least to HALF.
Today I got 2 eggs. The other day I got 3, and the other day I only got 1, so on average it's about half as good as it was last fall when I was getting 4 eggs almost every day. I still have enough to give to my mom and mother in law occasionally, but not enough to spread around the neighborhood.
They are still free ranging with BOSS and some corn as treats. They have Layena pellets in their coop, but they visit the baby's coop to eat the Flock Raiser. When we are out of Layena I will only be buying Flock Raiser for everyone.