probably about 1%, hold on, ill try find a site thatll give you your answer...
ok, i cant see ratios, but i found a site that says which pokemon hold which item, and there are other useful cheats as well, not sure if they are true, but whatever, try them out...
http://www.planetsilicon.co.uk/cheats/files/cheats-2755.aspx
Join this site...http://s14.invisionfree.com/ChaoticRoleplayRealm/index.php?
and this one...http://gameknot.com/?rfr=diezombie...when you sign up the second one, where it says referals by, type in diezombie