FDFIX vs. SSSYX

Last updated Jun 24, 2026

FDFIX (Fidelity Flex 500 Index Fund) and SSSYX (State Street Equity 500 Index Fund Class K) are both mutual funds - FDFIX is a Large Cap Blend Equities fund tracking the Fidelity U.S. Large Cap Index, while SSSYX is a S&P 500 fund tracking the S&P 500 Index. Both are passively managed. Over the past 5 years, FDFIX returned 13.53%/yr vs 13.57%/yr for SSSYX. With a 0.99 correlation, they move nearly in lockstep. FDFIX charges 0.00%/yr vs 0.02%/yr for SSSYX.

Performance

FDFIX vs. SSSYX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Fidelity Flex 500 Index Fund (FDFIX) and State Street Equity 500 Index Fund Class K (SSSYX). 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 9.64% return and SSSYX slightly higher at 9.78%.

FDFIX

• 1D: -0.38%
• 1M: 0.31%
• YTD: 9.64%
• 6M: 8.63%
• 1Y: 25.08%
• 3Y*: 21.26%
• 5Y*: 13.53%
• 10Y*: —

SSSYX

• 1D: -0.36%
• 1M: 0.10%
• YTD: 9.78%
• 6M: 8.78%
• 1Y: 25.47%
• 3Y*: 21.36%
• 5Y*: 13.57%
• 10Y*: 45.70%

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

FDFIX vs. SSSYX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
FDFIX Fidelity Flex 500 Index Fund	9.64%	17.59%	25.06%	26.27%	-18.10%	28.69%	18.46%	31.47%	-4.45%	14.41%
SSSYX State Street Equity 500 Index Fund Class K	9.78%	17.81%	24.99%	26.27%	-18.16%	28.51%	1,083.11%	31.38%	-4.38%	14.84%

Correlation

The correlation between FDFIX and SSSYX 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	0.99
Correlation (5Y) Calculated over the trailing 5-year period	1.00
Correlation (All Time) Calculated using the full available price history since Mar 9, 2017	0.99

The correlation between FDFIX and SSSYX has been stable across timeframes, ranging from 0.99 to 1.00 - a consistent structural relationship.

Return for Risk

FDFIX vs. SSSYX — Risk / Return Rank

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

FDFIX

FDFIX Risk / Return Rank: 61
FDFIX Sharpe Ratio Rank: 60
FDFIX Sortino Ratio Rank: 54
FDFIX Omega Ratio Rank: 56
FDFIX Calmar Ratio Rank: 65
FDFIX Martin Ratio Rank: 73

SSSYX

SSSYX Risk / Return Rank: 65
SSSYX Sharpe Ratio Rank: 63
SSSYX Sortino Ratio Rank: 57
SSSYX Omega Ratio Rank: 59
SSSYX Calmar Ratio Rank: 68
SSSYX 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.

FDFIX vs. SSSYX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Fidelity Flex 500 Index Fund (FDFIX) and State Street Equity 500 Index Fund Class K (SSSYX). 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.

	FDFIX	SSSYX	Difference
Sharpe ratio: Return per unit of total volatility	2.10	2.15	-0.05
Sortino ratio: Return per unit of downside risk	2.83	2.91	-0.07
Omega ratio: Gain probability vs. loss probability	1.38	1.39	-0.01
Calmar ratio: Return relative to maximum drawdown	2.95	3.02	-0.07
Martin ratio: Return relative to average drawdown	12.98	13.62	-0.64

FDFIX vs. SSSYX - Sharpe Ratio Comparison

The current FDFIX Sharpe Ratio is 2.10, which is comparable to the SSSYX Sharpe Ratio of 2.15. The chart below compares the historical Sharpe Ratios of FDFIX and SSSYX, 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

FDFIX vs. SSSYX - Drawdown Comparison

The maximum FDFIX drawdown since its inception was -33.77%, roughly equal to the maximum SSSYX drawdown of -33.77%. Use the drawdown chart below to compare losses from any high point for FDFIX and SSSYX.

Drawdown Indicators

	FDFIX	SSSYX	Difference
Max Drawdown Largest peak-to-trough decline	-33.77%	-33.77%	0.00%
Max Drawdown (1Y) Largest decline over 1 year	-8.99%	-8.88%	-0.11%
Max Drawdown (3Y) Largest decline over 3 years	-18.76%	-18.74%	-0.02%
Max Drawdown (5Y) Largest decline over 5 years	-24.51%	-24.49%	-0.02%
Max Drawdown (10Y) Largest decline over 10 years	—	-33.77%	—
Current Drawdown Current decline from peak	-1.70%	-1.72%	+0.02%
Average Drawdown Average peak-to-trough decline	-4.56%	-3.91%	-0.65%
Ulcer Index Depth and duration of drawdowns from previous peaks	2.03%	1.96%	+0.07%

Volatility

FDFIX vs. SSSYX - Volatility Comparison

Fidelity Flex 500 Index Fund (FDFIX) and State Street Equity 500 Index Fund Class K (SSSYX) have volatilities of 4.81% and 4.67%, 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	SSSYX	Difference
Volatility (1M) Calculated over the trailing 1-month period	4.81%	4.67%	+0.14%
Volatility (6M) Calculated over the trailing 6-month period	10.00%	9.83%	+0.17%
Volatility (1Y) Calculated over the trailing 1-year period	12.64%	12.49%	+0.15%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	17.05%	16.98%	+0.07%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	18.59%	121.18%	-102.59%

FDFIX vs. SSSYX - Expense Ratio Comparison

FDFIX has a 0.00% expense ratio, which is lower than SSSYX'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. SSSYX - Dividend Comparison

FDFIX's dividend yield for the trailing twelve months is around 1.04%, less than SSSYX's 1.31% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
FDFIX Fidelity Flex 500 Index Fund	1.04%	1.11%	1.26%	1.48%	1.70%	1.27%	1.52%	1.78%	2.16%	0.50%	0.00%	0.00%
SSSYX State Street Equity 500 Index Fund Class K	1.31%	1.44%	1.63%	1.78%	2.16%	2.76%	1.86%	4.44%	5.18%	5.94%	2.07%	1.84%

Frequently Asked Questions

Can I hold both FDFIX and SSSYX in my portfolio?

With a correlation of 1.00, FDFIX and SSSYX 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 SSSYX?

FDFIX has higher volatility (4.81%) compared to SSSYX (4.67%). In terms of maximum drawdown, FDFIX dropped -33.77% vs SSSYX's -33.77%.

Which has better risk-adjusted returns?

SSSYX currently has the higher Sharpe Ratio (2.15 vs 2.10), 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.