VMCIX vs. VIIIX

Last updated Jun 23, 2026

VMCIX (Vanguard Mid-Cap Index Fund Institutional Shares) and VIIIX (Vanguard Institutional Index Fund Institutional Plus Shares) are both mutual funds - VMCIX is a Mid Cap Blend Equities fund managed by Vanguard, while VIIIX is a S&P 500 fund tracking the S&P 500 Index. Over the past 10 years, VMCIX returned 11.67%/yr vs 15.65%/yr for VIIIX. Their correlation of 0.91 suggests significant overlap in exposure. VMCIX charges 0.04%/yr vs 0.02%/yr for VIIIX.

Performance

VMCIX vs. VIIIX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Vanguard Mid-Cap Index Fund Institutional Shares (VMCIX) 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, VMCIX achieves a 10.88% return, which is significantly higher than VIIIX's 10.19% return. Over the past 10 years, VMCIX has underperformed VIIIX with an annualized return of 11.67%, while VIIIX has yielded a comparatively higher 15.65% annualized return.

VMCIX

• 1D: 0.74%
• 1M: 2.62%
• YTD: 10.88%
• 6M: 9.30%
• 1Y: 19.28%
• 3Y*: 15.58%
• 5Y*: 8.43%
• 10Y*: 11.67%

VIIIX

• 1D: 1.09%
• 1M: 0.47%
• YTD: 10.19%
• 6M: 9.68%
• 1Y: 27.18%
• 3Y*: 21.39%
• 5Y*: 14.24%
• 10Y*: 15.65%

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

VMCIX vs. VIIIX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
VMCIX Vanguard Mid-Cap Index Fund Institutional Shares	10.88%	11.67%	14.68%	16.54%	-18.70%	24.53%	18.20%	31.04%	-9.25%	19.30%
VIIIX Vanguard Institutional Index Fund Institutional Plus Shares	10.19%	17.87%	26.29%	25.79%	-18.14%	28.69%	18.41%	31.48%	-4.41%	21.82%

Correlation

The correlation between VMCIX and VIIIX is 0.79, which is moderate. They share some common price drivers but move independently often enough to provide real diversification benefit when combined.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.79
Correlation (3Y) Calculated over the trailing 3-year period	0.83
Correlation (5Y) Calculated over the trailing 5-year period	0.89
Correlation (10Y) Calculated over the trailing 10-year period	0.91
Correlation (All Time) Calculated using the full available price history since May 21, 1998	0.91

The correlation between VMCIX and VIIIX shifts across timeframes, from 0.79 (1 year) to 0.91 (all time), reflecting how their relationship changes across market environments.

VMCIX vs. VIIIX - Sectors Allocation Comparison

Sectors	VMCIX	VIIIX
Technology	18.6%	39.1%
Industrials	17.9%	7.8%
Financial Services	12.8%	10.9%
Consumer Cyclical	8.6%	9.9%
Energy	8.5%	3.1%
Utilities	8.3%	2.1%
Healthcare	7.6%	8.3%
Real Estate	5.4%	1.8%
Consumer Defensive	4.8%	4.5%
Basic Materials	4.2%	1.7%
Communication Services	3.1%	10.7%

Return for Risk

VMCIX vs. VIIIX — Risk / Return Rank

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

VMCIX

VMCIX Risk / Return Rank: 37
VMCIX Sharpe Ratio Rank: 33
VMCIX Sortino Ratio Rank: 32
VMCIX Omega Ratio Rank: 30
VMCIX Calmar Ratio Rank: 44
VMCIX Martin Ratio Rank: 46

VIIIX

VIIIX Risk / Return Rank: 66
VIIIX Sharpe Ratio Rank: 64
VIIIX Sortino Ratio Rank: 59
VIIIX Omega Ratio Rank: 61
VIIIX Calmar Ratio Rank: 68
VIIIX Martin Ratio Rank: 79

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.

VMCIX vs. VIIIX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Vanguard Mid-Cap Index Fund Institutional Shares (VMCIX) 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.

	VMCIX	VIIIX	Difference
Sharpe ratio: Return per unit of total volatility	1.54	2.17	-0.63
Sortino ratio: Return per unit of downside risk	2.19	2.93	-0.74
Omega ratio: Gain probability vs. loss probability	1.27	1.39	-0.13
Calmar ratio: Return relative to maximum drawdown	2.42	3.04	-0.62
Martin ratio: Return relative to average drawdown	9.09	13.74	-4.66

VMCIX vs. VIIIX - Sharpe Ratio Comparison

The current VMCIX Sharpe Ratio is 1.54, which is comparable to the VIIIX Sharpe Ratio of 2.17. The chart below compares the historical Sharpe Ratios of VMCIX 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

VMCIX vs. VIIIX - Drawdown Comparison

The maximum VMCIX drawdown since its inception was -58.86%, which is greater than VIIIX's maximum drawdown of -55.18%. Use the drawdown chart below to compare losses from any high point for VMCIX and VIIIX.

Drawdown Indicators

	VMCIX	VIIIX	Difference
Max Drawdown Largest peak-to-trough decline	-58.86%	-55.18%	-3.68%
Max Drawdown (1Y) Largest decline over 1 year	-8.13%	-8.90%	+0.77%
Max Drawdown (3Y) Largest decline over 3 years	-18.93%	-18.75%	-0.18%
Max Drawdown (5Y) Largest decline over 5 years	-27.54%	-24.50%	-3.04%
Max Drawdown (10Y) Largest decline over 10 years	-39.30%	-33.79%	-5.51%
Current Drawdown Current decline from peak	-0.84%	-1.36%	+0.52%
Average Drawdown Average peak-to-trough decline	-7.96%	-10.00%	+2.04%
Ulcer Index Depth and duration of drawdowns from previous peaks	2.16%	1.96%	+0.20%

Volatility

VMCIX vs. VIIIX - Volatility Comparison

The current volatility for Vanguard Mid-Cap Index Fund Institutional Shares (VMCIX) is 4.45%, while Vanguard Institutional Index Fund Institutional Plus Shares (VIIIX) has a volatility of 4.77%. This indicates that VMCIX experiences smaller price fluctuations and is considered to be less risky than VIIIX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	VMCIX	VIIIX	Difference
Volatility (1M) Calculated over the trailing 1-month period	4.45%	4.77%	-0.32%
Volatility (6M) Calculated over the trailing 6-month period	9.87%	9.91%	-0.04%
Volatility (1Y) Calculated over the trailing 1-year period	12.77%	12.47%	+0.30%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	17.70%	16.99%	+0.71%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	18.95%	18.10%	+0.85%

VMCIX vs. VIIIX - Expense Ratio Comparison

VMCIX has a 0.04% 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

VMCIX vs. VIIIX - Dividend Comparison

VMCIX's dividend yield for the trailing twelve months is around 1.35%, less than VIIIX's 2.44% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
VIIIX Vanguard Institutional Index Fund Institutional Plus Shares	2.44%	2.11%	3.66%	2.66%	3.39%	4.79%	3.07%	2.86%	2.45%	1.84%	2.38%	2.47%
VMCIX Vanguard Mid-Cap Index Fund Institutional Shares	1.35%	1.52%	1.49%	1.51%	1.60%	1.12%	1.45%	1.48%	1.83%	1.36%	1.46%	1.48%

Frequently Asked Questions

Can I hold both VMCIX and VIIIX in my portfolio?

VMCIX and VIIIX have a correlation of 0.79, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, VMCIX or VIIIX?

VIIIX has higher volatility (4.77%) compared to VMCIX (4.45%). In terms of maximum drawdown, VMCIX dropped -58.86% vs VIIIX's -55.18%.

Which has better risk-adjusted returns?

VIIIX currently has the higher Sharpe Ratio (2.17 vs 1.54), 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.