11/02/2026
A Tale of Two I Funds
I'm going to write this up in an article so that I can address it completely and show all the calculations and documentation:
Old I Fund Index used by TSP: MSCI EAFE
New I Fund Index used by TSP: MSCI ACWI IMI ex USA ex China ex Hong Kong
Comparing returns for both of them from 2003 to 2025 (Obviously neither has been used by TSP for that full time continuously because of the switchover in 2024, but I'm comparing 23 years of the old vs 23 years of the new):
Compounded Annual Growth of Old I Fund 2003-2025: 7.77%
Compounded Annual Growth of New I Fund 2003-2025: 8.44%
Source: TSP and Morgan Stanley. Article will have links to all source data. So you math people can geek out on it all. And find any errors in my calculations.
Is the new I Fund better long-term? Yes! By almost 3/4 of 1 percent!