IEMG vs VWO: The South Korea Factor

Modelist Inc March 6, 2026

Introduction

When investors choose an emerging markets ETF, the two leading low-cost options are IEMG (iShares Core MSCI Emerging Markets ETF) and VWO (Vanguard FTSE Emerging Markets ETF). At first, they look pretty much interchangeable — both offer broad emerging market equity exposure at scale. But beneath the surface, a single country classification decision creates a meaningful and persistent performance difference between them.

That country is South Korea. MSCI classifies South Korea as an emerging market, giving it a ~13.3% weight in IEMG, because South Korea would not meet some accounting standards required by MSCI. By contrast, FTSE classifies South Korea as a developed market, meaning VWO holds exactly 0% in Korean equities. But this weight difference has become increasingly consequential as Korean semiconductor giants Samsung Electronics and SK hynix have ridden the AI boom to the stratosphere.

The Classification Gap

Let’s look a little more closely at the country weights in each index. IEMG tracks the MSCI Emerging Markets Investable Market Index (IMI), while VWO tracks the FTSE Emerging Markets All Cap China A Inclusion Index. The most significant divergence between these two index providers is their treatment of South Korea, shown below:

Because VWO excludes South Korea entirely, that 13.3% weight is redistributed across other countries — primarily China (+6.1pp), India (+3.2pp), and Taiwan (+2.2pp). This means investing in VWO instead of IEMG is implicitly a bet against Korean equities and in favor of heavier China and India exposure. To be clear these choices are somewhat arbitrary since by any economic metric Taiwan and South Korea are actually wealthier than many “developed” countries. That said, when you look at the effect these weightings have on returns in any given year the differences can be large.

The Holdings That Matter

This country-level difference ends up translating directly into specific stock exposures. Notably, Samsung Electronics (4.6% of IEMG) and SK hynix (2.6%) are the 2nd and 5th largest holdings in IEMG respectively — and they are completely absent from VWO! Together, these two Korean semiconductor companies account for nearly 7.1% of IEMG with zero representation in VWO.

Performance: The Scoreboard

Since 2013, the cumulative performance of IEMG and VWO has tracked closely, but with meaningful year-to-year divergences that derive from these country weight divergences. Over the 2013–2024 period the race between IEMG and VWO was genuinely close, with the two funds swapping cumulative leads several times. Because fees are nearly identical (0.09% vs 0.07%), the spread has been driven almost entirely by South Korea: when Korean equities led the broader EM universe, IEMG won; when they lagged, VWO won.

That dynamic reversed sharply in 2025. South Korea (EWY) surged 95% in a single year, driven by Samsung and SK hynix riding the global AI infrastructure buildout narrative. In 2025 alone, this allowed IEMG to outperform VWO by roughly 6.8 percentage points — erasing much of the accumulated underperformance from prior years.

Tracking the Spread

The cumulative return spread between IEMG and VWO tells the story clearly. As you can see in the chart below, VWO led for most of the past 15 years, with IEMG trailing VWO cumulatively by as much as ~2.3 percentage points at its worst. But the performance differential has snapped back violently — IEMG has recaptured roughly 8+ percentage points of relative performance since early 2025.

The Smoking Gun: Correlation Analysis

To confirm that South Korea is the primary driver of the IEMG–VWO performance gap, we calculated the rolling 1-year correlation between the daily IEMG–VWO return spread and South Korean equity returns (EWY). The results are striking.

The average correlation is 0.56, and it has been rising steadily — reaching 0.80 in recent months. This means that approximately 60–80% of the daily variation in the IEMG vs VWO performance gap can be explained by South Korean stock movements alone. No other single country difference between the two indexes comes close to explaining this.

Key Metrics at a Glance

Conclusion

The IEMG vs VWO decision is not completely about expense ratios or tracking error — it is fundamentally about whether you want South Korea in your emerging markets allocation or not. MSCI says yes (~13.3% of the index), FTSE says no (0%). When Korean equities outperform, IEMG wins. When they lag, VWO wins.

With Samsung Electronics and SK hynix positioned at the center of the global AI semiconductor supply chain, the South Korea allocation has become more consequential than it has ever been historically. Investors who chose IEMG over VWO have been handsomely rewarded in 2025–26, but this also means they are more exposed to Korean cyclical risk when the AI semiconductor cycle eventually turns. Keep in mind that the two funds have tracked each other closely over the full history — the South Korea allocation is the primary swing factor, not fees.

The bottom line: know what you own. The “emerging markets” label masks a 13.3 percentage point country allocation difference that has real performance consequences.

A Word of Caution on Fees and Forward-Looking Returns

It is worth noting that IEMG carries a marginally higher expense ratio than VWO (0.09% vs 0.07%), a fee gap of just 2 basis points per year – effectively a non-factor over any reasonable holding period. Despite this cost disadvantage, IEMG has recently outperformed VWO thanks to the explosive rally in South Korean semiconductor stocks. However, past performance is not indicative of future results, and there is no guarantee that this outperformance will persist.

The AI-driven rally that has propelled Samsung Electronics and SK hynix to extraordinary gains has also pushed valuations in the semiconductor sector to elevated levels. Whether these valuations are justified by future earnings growth or represent speculative excess is an open and unanswerable question.

Investors should weigh the switching costs carefully, as moving between these funds carries important tax consequences. In a scenario where South Korean equities mean-revert or underperform, VWO’s absence of Korean equity exposure would enable it to reassert its advantage. At the same time, if the Korean semiconductor boom has further to run, IEMG’s South Korea exposure could continue to be a tailwind — but that is a bet, not a certainty. Advisors should understand the structural differences between these two ETFs and make a deliberate, informed choice rather than switching to chase recent performance.

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