The TSP I Fund (International Stock Index Investment Fund) is getting renewed attention from federal employees. After years of underwhelming results, the fund posted a breakout year in 2025, prompting many investors to take a fresh look at what it actually is and how it fits into a retirement strategy.
At its core, the I Fund is designed to give federal employees exposure to international stocks; companies based outside the United States. Unlike the C Fund (which tracks large U.S. companies) or the S Fund (which focuses on smaller U.S. firms), the I Fund invests in businesses across global markets.
A Major Change Beneath the Surface
One of the biggest reasons the I Fund looks different today than it did just a few years ago is a significant benchmark change completed in 2024.
Historically, the I Fund tracked the MSCI EAFE Index, which included only large- and mid-sized companies in developed markets like Europe, Japan, and Australia. That meant no exposure to emerging markets and limited diversification overall.
That changed when the Federal Retirement Thrift Investment Board transitioned the fund to a much broader index: the MSCI All Country World Investable Market Index (ACWI IMI) ex U.S., China, and Hong Kong.
The impact of that shift is significant. The fund expanded from roughly 800 companies in 21 countries to more than 5,000 stocks across 44 countries, including both developed and emerging markets.
In practical terms, the I Fund is now far more diversified and better represents the global economy, though it still excludes China and Hong Kong due to policy considerations.
What the I Fund Invests In
Today’s TSP I Fund includes a mix of:
- Developed international markets (Europe, Japan, Canada, etc.)
- Emerging markets (such as Brazil, India, and others)
- Companies of all sizes—large, mid, and small cap
This broader exposure means the fund can capture growth opportunities outside the U.S., but it also introduces additional volatility tied to currency fluctuations, geopolitical events, and global economic cycles.
A Breakout Year in 2025
Performance is a big reason the I Fund is back in the spotlight.
In 2025, the I Fund delivered a 32.45% return, significantly outperforming the C Fund (17.85%) and S Fund (11.38%).
That kind of outperformance has led to a surge in investor interest and increased allocations, as federal employees look to capture international growth trends.
However, it’s important to keep that performance in context. The I Fund has historically gone through long stretches of underperformance compared to U.S. stocks, and its recent gains reflect a period where international markets have outpaced domestic ones.
Where the I Fund Fits
For federal employees, the I Fund plays a key role in diversification. It provides exposure to global markets that aren’t captured by the C and S Funds, helping spread risk across different economies.
But like any equity investment, it comes with trade-offs. Greater diversification can mean higher long-term opportunity, but also more short-term swings.
The Big Picture
The TSP I Fund isn’t the same fund it was a few years ago. With a broader index, expanded global reach, and renewed performance, it has evolved into a more comprehensive international investment option.
For federal employees reviewing their TSP allocations, understanding that evolution is critical. The recent surge in returns may be what’s grabbing attention, but the real story is how the fund itself has changed.
If you’re not sure whether your current mix still makes sense, or how the I Fund fits into your long-term strategy, reach out to a Federal Retirement Consultant (FRC®). A free analysis can help review your allocations, explore your options, and make sure you’re on track for retirement.
