These files have five columns of numbers separated by tabs.

The first column is the value-as-of month and the second column is the issue month. May 1941 is month 1 and they just go up from there.

The third column is the redemption value of a $25 bond of that issue in that month. The fourth column is the lifetime yield of that issue through that month.

The last column is the interest rate of that issue in that month. If there's a negative number in this column it means the rate hasn't been determined yet.

To get the EE bond data for the graph on this page, load the file named crv_ee.txt into a spreadsheet. Add a sixth column that divides the third column by $12.50, the initial investment for a $25 EE bond.

Next set a filter on the second column so it only shows month 681, which is January 1998. The sixth column now has the data for this graph.

Because I assume all dividends are reinvested, the spreadsheet has to track the shares owned month by month.

Leave three columns for the Vanguard data (date, price, dividend) and make the fourth column the number of shares owned.

The fifth column is the number of shares purchased. In months in which you add shares (on this chart, the share purchase occurs only in the first month, on my I bonds chart, share purchases occur every month) use 1 divided by that month's price as the number of shares purchased.

The sixth column is the number of shares obtained through reinvested dividends. It's the number of shares owned at the beginning of the month times the dividend rate divided by 12. You have to divide by 12 because the dividend rate is an annual rate, but you're adding shares monthly.

Once you know how many shares you have at the beginning of each month, just multiply that by the month's price column to get the value of the investment, which goes in the seventh column and is the number that ends up on the graph.