How Firecalc handles missing Treasury data
A belated response to some questions about why fiddling with the TIPS coupon would affect the results when you aren't investing in TIPS...
As TH points out, Firecalc gets testy when you fiddle with its TIPS but then don't follow through. (Sorry... I couldn't resist.)
As most folks know, there were no such things as 30 year Treasuries before 1925, and no such thing as 5 year Treasuries before 1953. Simply leaving those out would result in too little data for good calculations.
After discussions with whoever was paying attention back when this was all being done, we* decided to use the average of commercial paper and the theoretical TIPS calculation for missing years.
(* - The literary "we".)
The rationale for that is lost in the archives of the TMF RE forum and correspondence I no longer have.
If there is any consensus on a better approach(just use commercial paper?), I am glad to make the change. It's a simple change in the code.
Often uninformed, seldom undecided.
Twenty years from now you will be more disappointed by the things you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover. Mark Twain