Speaking as someone who used to work for Stonegate Farmers - not very. I think they used to have a range that was all double yolkers. Wouldn't swear to it - I just fixed the computers.
BTW - if you like eggs, never go to a chicken farm - the smell will put you off for life.
Went away on a course for a week a couple of weeks ago, and the hotel I was staying in managed to produce a double yolker fried egg every morning for me. Either clever frying or they got their eggs from some geneticaly modified super-chicken freak.
I used to pick up eggs in a chicken farm when i was young on a saturday morning before a trip down to the Goldstone.Some times we even got triples (f*** knows how they laid them) but the best ones were these eggs that never had a proper shell - We used to call them jellies ,it was just like a soft rubbery shell.God did we stink when we came home though.
Anything you want to know about eggs feel free to ask.