“This drift toward quantity instead of quality is largely distortion. Conformity is always too convenient? Quality means individuality, is therefore difficult. But unless we go deeper now, quantity at expense to quality will be our national tragedy—the rise of mediocrity into high places.”

Vol. VIII, p. 47ff.
Joannis Kepleri Astronomi Opera Omnia, ed. Christian Frisch (1858)

Shades of the World (1985)

Column, December 23, 2007, "The Gift Of Doing Very Little" http://www.washingtonpost.com/wp-dyn/content/article/2007/12/21/AR2007122101922.html at washingtonpost.com.
2000s

section 15
The Myth of Modernity (1946)

Source: Les Misérables

Source: Epistulae Morales ad Lucilium (Moral Letters to Lucilius), Letter XLV: On sophistical argumentation, Line 1

http://www.thisisnottingham.co.uk/forest/Forest-look-loan-market-void-left-Earnshaw-injury-says-Davies/article-2638035-detail/article.html
BD looks to the loan market after Earnshaw's injury and a winless start to the season.

No evidence that this phrasing is due to Stalin, and it does not appear in English translations of his philosphical works. Earliest English is found in 1979 in US defense industry, presumably defense consultant Thomas A. Callaghan Jr. The connection of sufficient quantitative change leading to qualitative change is found in Marxist philosophy, by Marx and Engels, drawing from Hegelian philosophy and Ancient Greek philosophy. Marx and Engels are quoted by Stalin, but this formulation appears to be a modern American form; see quantity for details.
Stalin may have said that way before World War II, there is evidence in his Russian-language books, for example here http://www.modernlib.ru/books/stalin_iosif_vissarionovich/tom_14/read_16/.
Misattributed
Variant: Quantity is quality.
Source: Re: "Quantity has a quality all its own" source? http://h-net.msu.edu/cgi-bin/logbrowse.pl?trx=vx&list=h-russia&month=1004&week=a&msg=ljEwsM4dMrpmUGVfI7EGqg, Tim Davenport, h-russia https://networks.h-net.org/h-russia, April 5, 2010