In the past I have been told, by someone at Winnebago, that Winnebago doesn't release production numbers.
Stumbled across this:
It's in their 2015 Annual Report.
Their 2008 report goes back another 5 years:
Gotta to go back one more chunk to see 2004, their best year ever:
Quite a roller coaster ride! (Why didn't I ever think to look it up? Silly me, asking someone at Winnebago!)
Winnebago Annual Reports