Gibbon famously said the period that followed the rule of Espaise in his two sons, so including Trajan and Hadrian, was when the condition of mankind was at its happiest. The whole of the Mediterranean is under a unitary power - Romans call it Maureen Nostrum, our sea. Different areas of the empire can start specialising in aspects of economic activity that they're particularly suited to. And so the economy really is by the standards of what had gone before, very, very golden in this period.