In this paper we study an \(L^{p}\) analogue of Bohr’s abscissae of summability for Dirichlet series. For polynomially bounded analytic functions in a strip with order function \(\mu \) , convexity of \(1/\mu \) is equivalent to approximate concavity of the abscissae in p. If \(\mu \) obeys a functional equation of the Selberg class type, this is equivalent to the Lindelöf hypothesis if \(\mu '(1/2)\) does not exist. Otherwise, \(\mu \) is everywhere differentiable (therefore subconvex) with quadratic decay near one.