After I saw the similarities and differences between DPD and the interest rate (see yesterday's post) I decided to plot the two against each other, like inflation versus unemployment on the Phillips Curve graph. So I went back to EconomPic, where Jake has a link to interest rate data from Robert J. Shiller's Irrational Exuberance. When I clicked Jake's link, download started automatically for the Excel file ie_data.xls.
The file contains two sheets with graphs, and one with data going back to 1871: stock dividends and a price index among others, and in column G the interest rate numbers.
A graph of Shiller's interest rate data going back to 1871 shows three longwave peaks. Not two:
The years between the first peak and the end of the first "secondary" peak match the years of the Long Depression.