We use 1980, 1990, and 1997 data on state lobbying registrations to examine
the diversity of interest communities on two dimensions: the range of subs
tantive interests and organizational types represented. The former has rema
ined quite stable over the last two decades while the level of relative ins
titutional representation has increased markedly We replicate and extend Lo
wery and Gray's (1998) analysis of four theoretical accounts oi temporal an
d spatial variations in levels of the latter-institutional dominance. Only
one of their four accounts-one emphasizing the role of interest system dens
ity in promoting direct lobbying by institutions-survives these tests. We c
onclude by discussing the implications of these findings for interest group
politics.