FSMDX vs. SSMKX

Last updated Jun 4, 2026

FSMDX (Fidelity Mid Cap Index Fund) and SSMKX (State Street Small/Mid Cap Equity Index Fund) are both Mid Cap Blend Equities funds. Over the past 10 years, FSMDX returned 11.69%/yr vs 12.48%/yr for SSMKX. With a 0.96 correlation, they move nearly in lockstep. FSMDX charges 0.03%/yr vs 0.04%/yr for SSMKX.

Performance

FSMDX vs. SSMKX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Fidelity Mid Cap Index Fund (FSMDX) and State Street Small/Mid Cap Equity Index Fund (SSMKX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, FSMDX achieves a 12.78% return, which is significantly lower than SSMKX's 14.17% return. Over the past 10 years, FSMDX has underperformed SSMKX with an annualized return of 11.69%, while SSMKX has yielded a comparatively higher 12.48% annualized return.

FSMDX

• 1D: 0.70%
• 1M: 4.12%
• YTD: 12.78%
• 6M: 12.57%
• 1Y: 22.14%
• 3Y*: 17.58%
• 5Y*: 8.41%
• 10Y*: 11.69%

SSMKX

• 1D: 1.00%
• 1M: 5.71%
• YTD: 14.17%
• 6M: 13.00%
• 1Y: 29.82%
• 3Y*: 20.36%
• 5Y*: 7.43%
• 10Y*: 12.48%

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

FSMDX vs. SSMKX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
FSMDX Fidelity Mid Cap Index Fund	12.78%	10.58%	15.55%	17.20%	-17.27%	22.56%	17.13%	30.53%	-9.38%	18.04%
SSMKX State Street Small/Mid Cap Equity Index Fund	14.17%	12.77%	17.20%	25.20%	-25.49%	12.38%	32.41%	27.82%	-9.02%	18.16%

Correlation

The correlation between FSMDX and SSMKX is 0.95, 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	0.95
Correlation (3Y) Calculated over the trailing 3-year period	0.96
Correlation (5Y) Calculated over the trailing 5-year period	0.96
Correlation (10Y) Calculated over the trailing 10-year period	0.96
Correlation (All Time) Calculated using the full available price history since Jan 5, 2016	0.96

The correlation between FSMDX and SSMKX has been stable across timeframes, ranging from 0.95 to 0.96 - a consistent structural relationship.

Return for Risk

FSMDX vs. SSMKX — Risk / Return Rank

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

FSMDX

FSMDX Risk / Return Rank: 43
FSMDX Sharpe Ratio Rank: 37
FSMDX Sortino Ratio Rank: 36
FSMDX Omega Ratio Rank: 33
FSMDX Calmar Ratio Rank: 56
FSMDX Martin Ratio Rank: 55

SSMKX

SSMKX Risk / Return Rank: 48
SSMKX Sharpe Ratio Rank: 42
SSMKX Sortino Ratio Rank: 40
SSMKX Omega Ratio Rank: 37
SSMKX Calmar Ratio Rank: 67
SSMKX Martin Ratio Rank: 57

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.

FSMDX vs. SSMKX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Fidelity Mid Cap Index Fund (FSMDX) and State Street Small/Mid Cap Equity Index Fund (SSMKX). 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.

	FSMDX	SSMKX	Difference
Sharpe ratio: Return per unit of total volatility	1.75	1.88	-0.13
Sortino ratio: Return per unit of downside risk	2.51	2.63	-0.12
Omega ratio: Gain probability vs. loss probability	1.30	1.32	-0.02
Calmar ratio: Return relative to maximum drawdown	2.87	3.16	-0.29
Martin ratio: Return relative to average drawdown	11.06	11.48	-0.42
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

FSMDX vs. SSMKX - Sharpe Ratio Comparison

The current FSMDX Sharpe Ratio is 1.75, which is comparable to the SSMKX Sharpe Ratio of 1.88. The chart below compares the historical Sharpe Ratios of FSMDX and SSMKX, 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

	FSMDX	SSMKX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	1.75	1.88	-0.13
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.46	0.34	+0.13
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.61	0.56	+0.04
Sharpe Ratio (All Time) Calculated using the full available price history	0.70	0.57	+0.13

Drawdowns

FSMDX vs. SSMKX - Drawdown Comparison

The maximum FSMDX drawdown since its inception was -40.35%, roughly equal to the maximum SSMKX drawdown of -41.65%. Use the drawdown chart below to compare losses from any high point for FSMDX and SSMKX.

Drawdown Indicators

	FSMDX	SSMKX	Difference
Max Drawdown Largest peak-to-trough decline	-40.35%	-41.65%	+1.30%
Max Drawdown (1Y) Largest decline over 1 year	-8.16%	-10.03%	+1.87%
Max Drawdown (3Y) Largest decline over 3 years	-20.92%	-26.31%	+5.39%
Max Drawdown (5Y) Largest decline over 5 years	-26.07%	-35.19%	+9.12%
Max Drawdown (10Y) Largest decline over 10 years	-40.35%	-41.65%	+1.30%
Current Drawdown Current decline from peak	0.00%	0.00%	0.00%
Average Drawdown Average peak-to-trough decline	-4.96%	-8.70%	+3.74%
Ulcer Index Depth and duration of drawdowns from previous peaks	2.11%	2.76%	-0.65%

Volatility

FSMDX vs. SSMKX - Volatility Comparison

The current volatility for Fidelity Mid Cap Index Fund (FSMDX) is 3.31%, while State Street Small/Mid Cap Equity Index Fund (SSMKX) has a volatility of 4.70%. This indicates that FSMDX experiences smaller price fluctuations and is considered to be less risky than SSMKX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	FSMDX	SSMKX	Difference
Volatility (1M) Calculated over the trailing 1-month period	3.31%	4.70%	-1.39%
Volatility (6M) Calculated over the trailing 6-month period	9.93%	12.35%	-2.42%
Volatility (1Y) Calculated over the trailing 1-year period	13.42%	16.90%	-3.48%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	18.26%	22.25%	-3.99%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	19.32%	22.26%	-2.94%

FSMDX vs. SSMKX - Expense Ratio Comparison

FSMDX has a 0.03% expense ratio, which is lower than SSMKX's 0.05% 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

FSMDX vs. SSMKX - Dividend Comparison

FSMDX's dividend yield for the trailing twelve months is around 0.98%, less than SSMKX's 4.47% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
FSMDX Fidelity Mid Cap Index Fund	0.98%	1.10%	2.46%	1.39%	2.07%	3.35%	2.34%	2.86%	2.21%	2.17%	2.23%	2.84%
SSMKX State Street Small/Mid Cap Equity Index Fund	4.47%	5.10%	2.12%	2.56%	17.09%	9.69%	1.47%	5.75%	3.68%	5.52%	1.30%	0.00%

Frequently Asked Questions

Can I hold both FSMDX and SSMKX in my portfolio?

With a correlation of 0.95, FSMDX and SSMKX 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, FSMDX or SSMKX?

SSMKX has higher volatility (4.70%) compared to FSMDX (3.31%). In terms of maximum drawdown, FSMDX dropped -40.35% vs SSMKX's -41.65%.

Which has better risk-adjusted returns?

SSMKX currently has the higher Sharpe Ratio (1.88 vs 1.75), 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.