Canals. The best study of the finance of canals is by J. R. Ward. According to Ward, the capital raised between 1755 and 1815 for canal construction was £17,201,000. This figure, with the exception of the Bridgewater canal (£300,000) refers to joint-stock canals. The figure is for England alone, in current prices, and does not cover pre-1755 investment in river improvement undertakings. A somewhat higher figure of £23,998,000 can be calculated based on Ginarlis and Pollard, who based their figures on Britain, not England. For my calculations, I have used the lower figure.

Turnpikes. The best available estimate of aggregate investment in turnpikes is by Ginarlis and Pollard. A calculation, based on their annual figures, brings the total investment for the period 1750–1810 to £19,962,000. The figures are of quasi-net investment; they refer only to turnpikes and not to other roads; and they give no estimates of pre-1750 investments. The figures are for Great Britain as a whole. Ginarlis and Pollard estimated that investment in turnpikes in Wales was 5 percent of the investment in England, and those in Scotland 20 percent, which means that the figure for England should be reduced to 80 percent of the British total. The reduced figure, referring to England only, of £15,969,600, is used here.