Quote by W. Edwards Deming
It is not necessary to change. Survival is not mandatory.
Another version (Dr. Deming in a letter to Mike Stoecklein):
"Survival is not compulsory.
Improvement is not compulsory.
But improvement is necessary for survival."
Please suggest source details if you know: book, page, year, online article address (url), correction (different author...), etc.. Thanks.