The construction of hypothetical benefit-cost ratios and internal rates of return for Normandy was given a great deal of attention in the text. Thus, there is no need to go over the construction of those series. The complete set of estimates is presented in Table A2.1. In the case of Provence, however, two different issues must be explored. Indeed, Chapter 7 left in the dark both how the estimate of increased irrigation was constructed and how canal construction accounts were put together.

INCREASES IN IRRIGATED AREAS IN PROVENCE

The studies of irrigation by J.-A. Barral offer good data for estimating the increase in total output as a result of irrigation because he investigated irrigated acreage thoroughly for each canal. According to Barral, in 1875 the total irrigated area for Provence was about 52,700 hectares, or 18 percent of the total cultivated area. To evaluate total output changes, we must know the increase in area irrigated, not only from the Durance (a figure that is available and presented in Table A2.2), but also from other rivers. The increase in irrigation from other sources is not known precisely, so I present two estimates. The first concerns the impact of the increase in Durance irrigation, while the second estimates the increase in output that would have occurred if irrigation from all sources had grown at the same rate as Durance irrigation.

Since irrigation at least doubled agricultural output, we know that the increase in output will be close to the ratio of newly irrigated area to total cultivated area.