Note, however, that the collapse in population was by no means uniform ... the Mediterranean urban centers that depended on Egyptian and North African wheat for their subsistence were absolutely hammered when the Bubonic plague reached Alexandria from the headwaters of the Nile ... and while wine and olive oil may be able to command quite a bit of bread in trade, its a bit hard to live off wine and olive oil alone.

By contrast, with the development of the heavy wheeled mouldboard plough, populations in northern Europe expanded substantially in the second half of the first millenium.

(And, of course, if you are engage in commercial slave plantation agriculture when the Mediterranean food distribution system is being hammered by repeated outbreaks of plague, enough basic staple foods to keep your slaves alive and working is a rapidly rising cost of business ... while if you rely on a local monopoly of force to extract a rent in kind from a peasant farmer, you can get in the business of having staple food to live off of and a surplus to sell.)

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.