Abstract. For a nite abelian p-group A of rank d = dim A pA, let M A ∶= log p A d be its (logarithmic) mean exponent. We study the behavior of the mean exponent of p-class groups in pro-p towers L K of number elds. Via a combination of results from analytic and algebraic number theory, we construct in nite tamely rami ed prop towers in which the mean exponent of p-class groups remains bounded. Several explicit examples are given with p = . Turning to group theory, we introduce an invariant M(G) attached to a nitely generated pro-p group G; when G = Gal(L K), where L is the Hilbert p-class eld tower of a number eld K, M(G) measures the asymptotic behavior of the mean exponent of p-class groups inside L K. We compare and contrast the behavior of this invariant in analytic versus non-analytic groups. We exploit the interplay of group-theoretical and number-theoretical perspectives on this invariant and explore some open questions that arise as a result, which may be of independent interest in group theory.