(Steven) Gould and (Niles) Eldridge seem to have published a lot together (and singly), so if you're going to cite particular assertions of theirs with particular numeric values, it would really help those of us who try to learn things if you could provide a specific reference -- so please provide the reference you got this from.
Gould did give the 99% figure according to Robert L. Carrol's
Patterns and Processes of Verterbrate Evolution. He gives the reference for this as p.84 of:
Gould, S.J. (1982) The meaning of punctuated equilibrium and its role in validating a hierarchical approach to macroevolution. In
Perspectives on Evolution, ed. R. Milkman, pp.83-104, Sunderland, Mass.: Sinauer Associated.