FDFIX vs. VIIIX

Last updated Jun 4, 2026

FDFIX (Fidelity Flex 500 Index Fund) and VIIIX (Vanguard Institutional Index Fund Institutional Plus Shares) are both Large Cap Blend Equities funds. Over the past 5 years, FDFIX returned 14.20%/yr vs 14.42%/yr for VIIIX. With a 1.00 correlation, they move nearly in lockstep. FDFIX charges 0.00%/yr vs 0.02%/yr for VIIIX.

Performance

FDFIX vs. VIIIX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Fidelity Flex 500 Index Fund (FDFIX) and Vanguard Institutional Index Fund Institutional Plus Shares (VIIIX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

The year-to-date returns for both investments are quite close, with FDFIX having a 11.53% return and VIIIX slightly higher at 11.70%.

FDFIX

• 1D: 0.22%
• 1M: 6.02%
• YTD: 11.53%
• 6M: 11.45%
• 1Y: 28.49%
• 3Y*: 22.62%
• 5Y*: 14.20%
• 10Y*: —

VIIIX

• 1D: 0.13%
• 1M: 5.80%
• YTD: 11.70%
• 6M: 11.74%
• 1Y: 28.99%
• 3Y*: 23.17%
• 5Y*: 14.42%
• 10Y*: 15.74%

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

FDFIX vs. VIIIX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
FDFIX Fidelity Flex 500 Index Fund	11.53%	17.59%	25.06%	26.27%	-18.10%	28.69%	18.46%	31.47%	-4.45%	14.41%
VIIIX Vanguard Institutional Index Fund Institutional Plus Shares	11.70%	17.87%	26.29%	25.79%	-18.14%	28.69%	18.41%	31.48%	-4.41%	14.85%

Correlation

The correlation between FDFIX and VIIIX is 1.00 - these two move nearly in lockstep. At this level, holding both provides almost no diversification benefit. If you already own one, adding the other does little to reduce portfolio risk.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	1.00
Correlation (3Y) Calculated over the trailing 3-year period	1.00
Correlation (5Y) Calculated over the trailing 5-year period	1.00
Correlation (All Time) Calculated using the full available price history since Mar 10, 2017	1.00

The correlation between FDFIX and VIIIX has been stable across timeframes, ranging from 1.00 to 1.00 - a consistent structural relationship.

Return for Risk

FDFIX vs. VIIIX — Risk / Return Rank

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

FDFIX

FDFIX Risk / Return Rank: 70
FDFIX Sharpe Ratio Rank: 72
FDFIX Sortino Ratio Rank: 64
FDFIX Omega Ratio Rank: 64
FDFIX Calmar Ratio Rank: 72
FDFIX Martin Ratio Rank: 80

VIIIX

VIIIX Risk / Return Rank: 73
VIIIX Sharpe Ratio Rank: 76
VIIIX Sortino Ratio Rank: 67
VIIIX Omega Ratio Rank: 67
VIIIX Calmar Ratio Rank: 74
VIIIX Martin Ratio Rank: 83

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.

FDFIX vs. VIIIX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Fidelity Flex 500 Index Fund (FDFIX) 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.

	FDFIX	VIIIX	Difference
Sharpe ratio Return per unit of total volatility	2.47	2.52	-0.05
Sortino ratio Return per unit of downside risk	3.34	3.42	-0.08
Omega ratio Gain probability vs. loss probability	1.45	1.46	-0.01
Calmar ratio Return relative to maximum drawdown	3.28	3.36	-0.07
Martin ratio Return relative to average drawdown	14.96	15.69	-0.74
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

FDFIX vs. VIIIX - Sharpe Ratio Comparison

The current FDFIX Sharpe Ratio is 2.47, which is comparable to the VIIIX Sharpe Ratio of 2.52. The chart below compares the historical Sharpe Ratios of FDFIX 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.

Sharpe Ratios by Period

	FDFIX	VIIIX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	2.47	2.52	-0.05
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.84	0.86	-0.02
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	—	0.87	—
Sharpe Ratio (All Time) Calculated using the full available price history	0.82	0.50	+0.33

Drawdowns

FDFIX vs. VIIIX - Drawdown Comparison

The maximum FDFIX drawdown since its inception was -33.77%, smaller than the maximum VIIIX drawdown of -55.18%. Use the drawdown chart below to compare losses from any high point for FDFIX and VIIIX.

Drawdown Indicators

	FDFIX	VIIIX	Difference
Max Drawdown Largest peak-to-trough decline	-33.77%	-55.18%	+21.41%
Max Drawdown (1Y) Largest decline over 1 year	-8.99%	-8.90%	-0.09%
Max Drawdown (3Y) Largest decline over 3 years	-18.76%	-18.75%	-0.01%
Max Drawdown (5Y) Largest decline over 5 years	-24.51%	-24.50%	-0.01%
Max Drawdown (10Y) Largest decline over 10 years	—	-33.79%	—
Current Drawdown Current decline from peak	0.00%	0.00%	0.00%
Average Drawdown Average peak-to-trough decline	-4.58%	-10.02%	+5.44%
Ulcer Index Depth and duration of drawdowns from previous peaks	1.97%	1.90%	+0.07%

Volatility

FDFIX vs. VIIIX - Volatility Comparison

Fidelity Flex 500 Index Fund (FDFIX) and Vanguard Institutional Index Fund Institutional Plus Shares (VIIIX) have volatilities of 2.92% and 2.83%, respectively, indicating that both stocks experience similar levels of price fluctuations. This suggests that the risk associated with both stocks, as measured by volatility, is nearly the same. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	FDFIX	VIIIX	Difference
Volatility (1M) Calculated over the trailing 1-month period	2.92%	2.83%	+0.09%
Volatility (6M) Calculated over the trailing 6-month period	9.03%	8.97%	+0.06%
Volatility (1Y) Calculated over the trailing 1-year period	11.96%	11.86%	+0.10%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	16.95%	16.89%	+0.06%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	18.59%	18.06%	+0.53%

FDFIX vs. VIIIX - Expense Ratio Comparison

FDFIX has a 0.00% expense ratio, which is lower than VIIIX's 0.02% expense ratio. Despite the difference, both funds are considered low-cost compared to the broader market, where average expense ratios usually range from 0.3% to 0.9%.

Dividends

FDFIX vs. VIIIX - Dividend Comparison

FDFIX's dividend yield for the trailing twelve months is around 1.03%, less than VIIIX's 2.41% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
FDFIX Fidelity Flex 500 Index Fund	1.03%	1.11%	1.26%	1.48%	1.70%	1.27%	1.52%	1.78%	2.16%	0.50%	0.00%	0.00%
VIIIX Vanguard Institutional Index Fund Institutional Plus Shares	2.41%	2.11%	3.66%	2.66%	3.39%	4.79%	3.07%	2.86%	2.45%	1.84%	2.38%	2.47%

Frequently Asked Questions

Can I hold both FDFIX and VIIIX in my portfolio?

With a correlation of 1.00, FDFIX 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, FDFIX or VIIIX?

FDFIX has higher volatility (2.92%) compared to VIIIX (2.83%). In terms of maximum drawdown, FDFIX dropped -33.77% vs VIIIX's -55.18%.

Which has better risk-adjusted returns?

VIIIX currently has the higher Sharpe Ratio (2.52 vs 2.47), 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.