Which is why in "fusion" bombs the majority of energy still comes from fission. The fusion reaction is a neutron source to boost the efficiency of the fission reaction. A pure fusion bomb, if one could ever trigger such a thing without fission, would not be very efficient.
For "boosted fission" and early thermonuclear bomb designs yes, but not so for the more evolved thermonuclear designs. Navajo (Operation Redwing, 1956) was 95% fusion, Tsar bomba (1961) was 97% fusion, Housatonic (Operation Dominic, 1962) was 99.9% fusion.
