PS Dave, not everybody supplements their chickens' lighting. Some chickens do lay through the winter, and most hens lay through the winter in their first year of laying (I hear).
Some breeds are better about winter laying than others. My Gold Comets are laying, for instance, though my AustraWhite and Buckeye have not started, and may not til spring. They are living beings, not machines, so everything is variable!
The only reason to add the light is to induce them to lay (unless you need to see things yourself in the dark coop at night). Some folks feel it's better to let them have a rest, allowing the sun to govern their laying patterns. There is some suspicion that forcing laying year round may shorten their lifespan or cause illness (but no clear proof). It's a periodic discussion here, with some folks having very strong opinions. It's a matter of split opinion in our community.