I just downloaded Michael Grant’s “The Jews in the Roman empire “ and in the introduction he writes
“Numerically, taken over the whole earth, they were fewer in those days than they are now – perhaps eight million as against fourteen million today. But no less than seven of these eight million were in the Roman empire, where they constituted between six and nine per cent of the population – in the eastern provinces, the percentage was perhaps as high as twenty.”
So more like 7.5% not 15%
Thanks Cr.