VMGAX vs. VIIIX

Last updated Jun 24, 2026

VMGAX (Vanguard Mega Cap Growth Index Fund Institutional Shares) and VIIIX (Vanguard Institutional Index Fund Institutional Plus Shares) are both mutual funds - VMGAX is a Large Cap Growth Equities fund managed by Vanguard, while VIIIX is a S&P 500 fund tracking the S&P 500 Index. Over the past 10 years, VMGAX returned 19.24%/yr vs 15.87%/yr for VIIIX. Their correlation of 0.94 suggests significant overlap in exposure. VMGAX charges 0.06%/yr vs 0.02%/yr for VIIIX.

Performance

VMGAX vs. VIIIX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Vanguard Mega Cap Growth Index Fund Institutional Shares (VMGAX) and Vanguard Institutional Index Fund Institutional Plus Shares (VIIIX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, VMGAX achieves a 5.90% return, which is significantly lower than VIIIX's 9.78% return. Over the past 10 years, VMGAX has outperformed VIIIX with an annualized return of 19.24%, while VIIIX has yielded a comparatively lower 15.87% annualized return.

VMGAX

• 1D: -1.41%
• 1M: -1.82%
• YTD: 5.90%
• 6M: 4.57%
• 1Y: 24.29%
• 3Y*: 24.22%
• 5Y*: 14.45%
• 10Y*: 19.24%

VIIIX

• 1D: -0.37%
• 1M: 0.10%
• YTD: 9.78%
• 6M: 8.78%
• 1Y: 25.51%
• 3Y*: 21.80%
• 5Y*: 13.75%
• 10Y*: 15.87%

*Multi-year figures are annualized to reflect compound growth (CAGR)

VMGAX vs. VIIIX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
VMGAX Vanguard Mega Cap Growth Index Fund Institutional Shares	5.90%	20.73%	32.98%	51.57%	-33.55%	28.50%	41.02%	37.54%	-2.86%	29.49%
VIIIX Vanguard Institutional Index Fund Institutional Plus Shares	9.78%	17.87%	26.29%	25.79%	-18.14%	28.69%	18.41%	31.48%	-4.41%	21.82%

Correlation

The correlation between VMGAX and VIIIX is 0.92, indicating a strong positive relationship between their price movements. Combining them offers limited diversification - they tend to fall together during downturns.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.92
Correlation (3Y) Calculated over the trailing 3-year period	0.92
Correlation (5Y) Calculated over the trailing 5-year period	0.94
Correlation (10Y) Calculated over the trailing 10-year period	0.92
Correlation (All Time) Calculated using the full available price history since Dec 27, 2007	0.94

The correlation between VMGAX and VIIIX has been stable across timeframes, ranging from 0.92 to 0.94 - a consistent structural relationship.

Return for Risk

VMGAX vs. VIIIX — Risk / Return Rank

Compare risk-adjusted metric ranks to identify better-performing investments over the past 12 months.

VMGAX

VMGAX Risk / Return Rank: 27
VMGAX Sharpe Ratio Rank: 32
VMGAX Sortino Ratio Rank: 29
VMGAX Omega Ratio Rank: 29
VMGAX Calmar Ratio Rank: 20
VMGAX Martin Ratio Rank: 23

VIIIX

VIIIX Risk / Return Rank: 65
VIIIX Sharpe Ratio Rank: 64
VIIIX Sortino Ratio Rank: 57
VIIIX Omega Ratio Rank: 59
VIIIX Calmar Ratio Rank: 68
VIIIX Martin Ratio Rank: 78

The rank (0–100) shows how this investment's returns compare to the risk taken. Higher = better. Based on the past 12 months of data, combining Sharpe, Sortino, and other metrics used by quantitative funds and institutional investors.

VMGAX vs. VIIIX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Vanguard Mega Cap Growth Index Fund Institutional Shares (VMGAX) and Vanguard Institutional Index Fund Institutional Plus Shares (VIIIX). Risk-adjusted metrics are performance indicators that assess an investment's returns in relation to its risk, enabling a more accurate comparison of different investment options.

Values are calculated on a 1-year rolling basis and updated daily. Risk-adjusted metrics are more stable over longer periods — use the period switch above to explore them.

	VMGAX	VIIIX	Difference
Sharpe ratio: Return per unit of total volatility	1.50	2.15	-0.65
Sortino ratio: Return per unit of downside risk	2.06	2.91	-0.85
Omega ratio: Gain probability vs. loss probability	1.26	1.39	-0.13
Calmar ratio: Return relative to maximum drawdown	1.54	3.02	-1.47
Martin ratio: Return relative to average drawdown	5.22	13.62	-8.40

VMGAX vs. VIIIX - Sharpe Ratio Comparison

The current VMGAX Sharpe Ratio is 1.50, which is lower than the VIIIX Sharpe Ratio of 2.15. The chart below compares the historical Sharpe Ratios of VMGAX and VIIIX, calculated using daily returns over the previous 12 months. A higher Sharpe Ratio indicates better risk-adjusted performance relative to the risk-free rate.

Drawdowns

VMGAX vs. VIIIX - Drawdown Comparison

The maximum VMGAX drawdown since its inception was -47.97%, smaller than the maximum VIIIX drawdown of -55.18%. Use the drawdown chart below to compare losses from any high point for VMGAX and VIIIX.

Drawdown Indicators

	VMGAX	VIIIX	Difference
Max Drawdown Largest peak-to-trough decline	-47.97%	-55.18%	+7.21%
Max Drawdown (1Y) Largest decline over 1 year	-16.78%	-8.90%	-7.88%
Max Drawdown (3Y) Largest decline over 3 years	-23.45%	-18.75%	-4.70%
Max Drawdown (5Y) Largest decline over 5 years	-36.03%	-24.50%	-11.53%
Max Drawdown (10Y) Largest decline over 10 years	-36.03%	-33.79%	-2.24%
Current Drawdown Current decline from peak	-5.12%	-1.72%	-3.40%
Average Drawdown Average peak-to-trough decline	-7.43%	-10.00%	+2.57%
Ulcer Index Depth and duration of drawdowns from previous peaks	4.95%	1.97%	+2.98%

Volatility

VMGAX vs. VIIIX - Volatility Comparison

Vanguard Mega Cap Growth Index Fund Institutional Shares (VMGAX) has a higher volatility of 6.81% compared to Vanguard Institutional Index Fund Institutional Plus Shares (VIIIX) at 4.68%. This indicates that VMGAX's price experiences larger fluctuations and is considered to be riskier than VIIIX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	VMGAX	VIIIX	Difference
Volatility (1M) Calculated over the trailing 1-month period	6.81%	4.68%	+2.13%
Volatility (6M) Calculated over the trailing 6-month period	13.71%	9.84%	+3.87%
Volatility (1Y) Calculated over the trailing 1-year period	17.27%	12.50%	+4.77%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	22.86%	16.98%	+5.88%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	21.99%	18.11%	+3.88%

VMGAX vs. VIIIX - Expense Ratio Comparison

VMGAX has a 0.06% expense ratio, which is higher than VIIIX's 0.02% expense ratio. However, both funds are considered low-cost compared to the broader market, where average expense ratios usually range from 0.3% to 0.9%.

Dividends

VMGAX vs. VIIIX - Dividend Comparison

VMGAX's dividend yield for the trailing twelve months is around 0.34%, less than VIIIX's 2.45% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
VIIIX Vanguard Institutional Index Fund Institutional Plus Shares	2.45%	2.11%	3.66%	2.66%	3.39%	4.79%	3.07%	2.86%	2.45%	1.84%	2.38%	2.47%
VMGAX Vanguard Mega Cap Growth Index Fund Institutional Shares	0.34%	0.36%	0.44%	0.51%	0.71%	0.42%	0.65%	0.86%	1.13%	1.23%	1.53%	1.44%

Frequently Asked Questions

Can I hold both VMGAX and VIIIX in my portfolio?

With a correlation of 0.92, VMGAX and VIIIX move almost identically. Holding both adds very little diversification - you're essentially doubling your position in the same market segment. Choosing one is usually more capital-efficient.

Which is riskier, VMGAX or VIIIX?

VMGAX has higher volatility (6.81%) compared to VIIIX (4.68%). In terms of maximum drawdown, VMGAX dropped -47.97% vs VIIIX's -55.18%.

Which has better risk-adjusted returns?

VIIIX currently has the higher Sharpe Ratio (2.15 vs 1.50), meaning it's delivered slightly more return per unit of risk over the trailing 12 months. However, this ranking shifts over time - use the Risk/Return Score above for a more comprehensive view that combines Sharpe, Sortino, and other measures used by quantitative funds.