preposition after 'instrumental'

the adj. instrumental is often followed by 'in + participium praesentis (v+ing)'. But this only applies when discussing processes, rather than nouns. What do we do when discussing something which is instrumental of an institution (e.g. "instrumental [adj.] human culture", or "instrumental [adj.] democracy")? should I use 'for' or 'to' as an adj? I found both in a Google Books search. is one of them more grammatically correct, common or elegant?

Instrumental in is indeed used mostly (but not only) with adjectives derived from verbs, such as -ing forms or adjectives with such suffixes as -tion, -ance, -ment and the like (e.g. formation, performance, achievement).

As for your examples, I think to is more frequent than for . I would definitely say:

instrumental to democracy; instrumental to human culture

Gngram finds instances of both "instrumental to" and "instrumental for", but gives preference to the construction with "to".

This site (lingohelp) will give you the percentage in which the preposition in, to, for, of (I wrote them in the order of their frequency) are used with instrumental.

Also, "instrumental for something" seems to put emphasis on the accomplished goal, whereas "instrumental to something" seems to stress the crucial importance of the factor it describes in achieving something.