Bodin was after Martín de Azpilicueta, who had alluded to the issue in 1556 (something noticed also by Gomara in his unpublished Annals), an early observer that the rise in prices was due in large part to the influx of precious metals. Analysing the phenomenon, amongst other factors he pointed to the relationship between the amount of goods and the amount of money in circulation. The debates of the time laid the foundation for the "quantity theory of money". Bodin mentioned other factors: population increase, trade, the possibility of economic migration, and consumption that he saw as profligate.