Correct.

But the entire purpose of the Imperium (at least IMTU) is to protect the Member Worlds from external aggression. My Imperium is much more like the North Atlantic Treaty Organization than it is a government in the usual sense. The Imperial Defense Tax is just that - a tax paid by the Member Worlds to finance protection of themselves from threats originating outside their own borders. When you trace the expenditures all the way out, these revenues prove to be spent in support of that goal.

The Imperial Navy and Marines are the cutting edge, equivalent to the forces the U.S. currently has on deployment as well as those ready for immediate use. The equivalent of the U.S. reserve and National Gaurd units as well as training and support bases withint the continental U.S. is represented by the Imperial Reserve and all the "civilian" infrastructure which can be militarized in the event of war, all of which is financed from the 33% spent on "local prosperity and welfare." The 33% going to the Imperial Treasury comes back down as funding for deep-support projects, equivalent to U.S. endeavors such as DARPA, ROTC programs, military aid to allies, etc.