Upgradation is one of those redundant words that probably grew in the fertile fields of corporate self-importance. After all, the existing nouns "upgrade" and "upgrading" seem downright wimpy compared to the muscular "upgradation" with its four syllables and "-ation" suffix.

This redundancy may explain why upgradation isn't in any dictionary (at least those that I have, including the OED 2; if you see it in a dictionary, let me know). However, a case can be made that it should be in the dictionaries because the word is both old and popular.

For evidence of its longevity, I managed to track it back to at least the following citation from 1979:

"The protocol also envisages the possibility of continuous technological upgradation in the existing fields of manufacture." —"USSR - Machine Building," BBC Summary of World Broadcasts, November 28, 1979

For evidence of its popularity, I checked through the Lexis-Nexis database of newspapers, magazines, and other media and found thousands of citations. However, the pattern of these citations is interesting. There were only 72 from 1979 to 1989. Then the numbers look like this:

1990 - 13
1991 - 10
1992 - 31
1993 - 46
1994 - 55
1995 - 44
1996 - 77
1997 - 483
1998 - 908
1999 - 853
2000 - 1,028

As you can see, for some reason usage of the word exploded in 1997 - 1998 and has continued apace. So if upgradation isn't in any dictionary, it's likely because its popularity is relatively recent.