For 1996, latest year of published data:
All returns 120,351,208
Itemized Ded 35,414,589 1040A 24,579,173 1040EZ 21,196,154 1040PC 8,310,882
Note you can file the long form w/o itemizing.
Note also these are returns. Any could reflect more than one person in a filing unit. With a little digging one could estimate the % of the pop reflected in returns that itemized.
I heard on the radio last week that only 30% of the pop files the long form. This was in the context of a radio promo for a local org that helps low income families deal with IRS which is after people who may be improperly filing for the EITC. it also helps people who have no idea they are eligible. (my sister never knew, for ex)
anyway, i checked out the IRS site but that stat is not easy to deduce from the tangled pathetic morass of info and stats on that site.
so, wondering if anyone here knows the numbers.