Dear DIgby,

it was fluctuating during the period : each department sent the majority of conscripts to two or three infantry and cavalry regiments, but the regiments could change at each conscription, and very frequently after 1808 (perhaps dependng on the uneven level of loss per regiment, or the necessity to create new regiments to replace the ones in Spain).
So one year a regiment had a defined local origin, that will change 3 or 4 years later, plus the unavoidable "minority".

Richard Darnaud had started a superb database on regiment per area (see link), but the display is organised by regiment / date / department, so tyou will have to contact him to obtain it by department / date / regiment (or browse it through and reedit your Napoléon's regiment dictionnary :) )

Kind regards,

Jean