There are potentially two broad reasons for the dramatic success of water control, at least at the local level, after the Revolution. On the one hand, demand for improved land may have increased because land may have become scarce after 1815. On the other hand, supply conditions may also have changed because the costs of improvements may have dramatically fallen during the Revolution. Both could have been equally due to changes in technology, institutions, or relative prices. In this chapter, I begin the task of discriminating between these hypotheses by constructing a framework to evaluate the returns to improvement and by examining relative price data.

I shall begin by examining the supply of improved land. The lack of water control development in the eighteenth century might be explained by institutional or technological factors that could have affected supply decisions. For example, as suggested earlier, during the eighteenth century, institutions might have raised the cost of development enough to discourage investment. Another explanation relies on technical change. Perhaps technological constraints hindered water control before the Revolution, while breakthroughs in the period between 1789 and 1820 could explain the sudden success of improvement projects in the nineteenth century.

The demand for improved land could also have changed significantly over time. French economic historians have long investigated the relationship between population and prices. To a large extent they have concluded that, until the middle of the eighteenth century at least, French society was caught in a Malthusian system: Wages were low and goods were dear in periods of high population. Increased population thus corresponded to periods of relative scarcity of food and therefore of land.