Where are those numbers from?
That's a bit simplistic. Central authority had already collapsed by 1991 and intense fighting had been going since about 1988. The Somali state was very progressive from 1969-1978, expanding roads, increasing literacy (which was only 7% and quickly shot up to 50%, that 24% - 38% gap seems unreal, I'd like to see the source for that), relocating large numbers of refugees (over a million from the Ogadeen and Hurd areas), providing large scale food aid during drought, saving many lives. The Somali state was key in providing support during the big drought of 73-74.
It is true things had decayed in the 80s, largely due to heavy foreign debts, the Saudi boycott of Somali livestock, and the decline of production in industry and agriculture. Too much was spent on the military to defend against the Ethiopian threat. But to summarize all this as government being worse for Somalia than no government is rather facile. Everything I've read about infrastructure (and Somalia preoccupies most of my time these days) points to its decay since the early 1990s.
One must consider also, that in Puntland & the territory encompassing Berbera & Hargeisa, that a functional government has pretty much existed but has not been recognized by the international community. This area, former British Somaliland, has strong commercial ties with the Arab world and surrounding states.
But overall you're correct than in the Benadir area and around the Juba & Shabelle rivers the occupation has been agriculture, not pastoralism, which is more hierarchical and amenable to government. There is a culture gap between the four pastoralist clan families (of Samaale/Cushitic stock) - Hawiye, Darood, Isaaq & Dir, and the sedentary/agriculturalist Rahanwayn-Digil who live in the South and who are of mixed Bantu/Cushitic stock.