Within the context of the isovector-pairing SO(5) model, three methods
measuring numbers of different kinds of nucleon pairs are discussed.
Though methods do not give the same results, the odd-even staggering i
n pair numbers in even-even and odd-odd N=Z nuclei and the reduction o
f the np-pair number with increasing T-z is observed in all three proc
edures. (C) 1997 Elsevier Science B.V.