I take my empirical doubling time from the average returns on investment in the Western world; that is the correct time-discounting to use in our current environment, as computed by the collective intelligence of all the investors on Earth.

I already observed:

The prevailing interest rate is normally not much of a factor - since money is only instrumentally valuable.

I do not think that interest rates are really a reflection of human temporal discounting. Why would anyone think that they were?