FLXSX vs. BOSOX

Last updated Jun 4, 2026

FLXSX (Fidelity Flex Small Cap Index Fund) and BOSOX (Boston Trust Small Cap Fund) are both Small Cap Blend Equities funds. Over the past 5 years, FLXSX returned 6.27%/yr vs 4.92%/yr for BOSOX. Their correlation of 0.92 suggests significant overlap in exposure. FLXSX charges 0.00%/yr vs 1.00%/yr for BOSOX.

Performance

FLXSX vs. BOSOX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Fidelity Flex Small Cap Index Fund (FLXSX) and Boston Trust Small Cap Fund (BOSOX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, FLXSX achieves a 17.21% return, which is significantly higher than BOSOX's 6.63% return.

FLXSX

• 1D: 0.33%
• 1M: 3.96%
• YTD: 17.21%
• 6M: 16.56%
• 1Y: 38.39%
• 3Y*: 17.93%
• 5Y*: 6.27%
• 10Y*: —

BOSOX

• 1D: 0.80%
• 1M: 2.85%
• YTD: 6.63%
• 6M: 4.71%
• 1Y: 6.71%
• 3Y*: 7.74%
• 5Y*: 4.92%
• 10Y*: 10.23%

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

FLXSX vs. BOSOX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
FLXSX Fidelity Flex Small Cap Index Fund	17.21%	12.02%	11.67%	17.11%	-20.29%	14.84%	20.06%	25.69%	-11.13%	14.28%
BOSOX Boston Trust Small Cap Fund	6.63%	-4.04%	12.52%	10.09%	-9.05%	28.10%	8.27%	38.35%	-6.01%	11.85%

Correlation

The correlation between FLXSX and BOSOX is 0.80, 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	0.80
Correlation (3Y) Calculated over the trailing 3-year period	0.88
Correlation (5Y) Calculated over the trailing 5-year period	0.90
Correlation (All Time) Calculated using the full available price history since Mar 10, 2017	0.92

The correlation between FLXSX and BOSOX shifts across timeframes, from 0.80 (1 year) to 0.92 (all time), reflecting how their relationship changes across market environments.

Return for Risk

FLXSX vs. BOSOX — Risk / Return Rank

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

FLXSX

FLXSX Risk / Return Rank: 54
FLXSX Sharpe Ratio Rank: 49
FLXSX Sortino Ratio Rank: 46
FLXSX Omega Ratio Rank: 40
FLXSX Calmar Ratio Rank: 73
FLXSX Martin Ratio Rank: 59

BOSOX

BOSOX Risk / Return Rank: 7
BOSOX Sharpe Ratio Rank: 6
BOSOX Sortino Ratio Rank: 7
BOSOX Omega Ratio Rank: 6
BOSOX Calmar Ratio Rank: 7
BOSOX Martin Ratio Rank: 7

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.

FLXSX vs. BOSOX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Fidelity Flex Small Cap Index Fund (FLXSX) and Boston Trust Small Cap Fund (BOSOX). 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.

	FLXSX	BOSOX	Difference
Sharpe ratio: Return per unit of total volatility	2.08	0.53	+1.55
Sortino ratio: Return per unit of downside risk	2.86	0.89	+1.96
Omega ratio: Gain probability vs. loss probability	1.34	1.10	+0.24
Calmar ratio: Return relative to maximum drawdown	3.35	0.74	+2.61
Martin ratio: Return relative to average drawdown	11.73	2.22	+9.51
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

FLXSX vs. BOSOX - Sharpe Ratio Comparison

The current FLXSX Sharpe Ratio is 2.08, which is higher than the BOSOX Sharpe Ratio of 0.53. The chart below compares the historical Sharpe Ratios of FLXSX and BOSOX, 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

	FLXSX	BOSOX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	2.08	0.53	+1.55
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.28	0.28	0.00
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	—	0.53	—
Sharpe Ratio (All Time) Calculated using the full available price history	0.42	0.43	-0.01

Drawdowns

FLXSX vs. BOSOX - Drawdown Comparison

The maximum FLXSX drawdown since its inception was -41.72%, smaller than the maximum BOSOX drawdown of -51.32%. Use the drawdown chart below to compare losses from any high point for FLXSX and BOSOX.

Drawdown Indicators

	FLXSX	BOSOX	Difference
Max Drawdown Largest peak-to-trough decline	-41.72%	-51.32%	+9.60%
Max Drawdown (1Y) Largest decline over 1 year	-12.25%	-10.69%	-1.56%
Max Drawdown (3Y) Largest decline over 3 years	-27.48%	-22.36%	-5.12%
Max Drawdown (5Y) Largest decline over 5 years	-31.88%	-22.36%	-9.52%
Max Drawdown (10Y) Largest decline over 10 years	—	-36.79%	—
Current Drawdown Current decline from peak	-0.19%	-6.67%	+6.48%
Average Drawdown Average peak-to-trough decline	-10.44%	-7.27%	-3.17%
Ulcer Index Depth and duration of drawdowns from previous peaks	3.48%	3.57%	-0.09%

Volatility

FLXSX vs. BOSOX - Volatility Comparison

Fidelity Flex Small Cap Index Fund (FLXSX) has a higher volatility of 5.03% compared to Boston Trust Small Cap Fund (BOSOX) at 3.90%. This indicates that FLXSX's price experiences larger fluctuations and is considered to be riskier than BOSOX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	FLXSX	BOSOX	Difference
Volatility (1M) Calculated over the trailing 1-month period	5.03%	3.90%	+1.13%
Volatility (6M) Calculated over the trailing 6-month period	14.19%	10.08%	+4.11%
Volatility (1Y) Calculated over the trailing 1-year period	19.72%	15.10%	+4.62%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	22.66%	17.82%	+4.84%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	24.00%	19.56%	+4.44%

FLXSX vs. BOSOX - Expense Ratio Comparison

FLXSX has a 0.00% expense ratio, which is lower than BOSOX's 1.00% expense ratio.

Dividends

FLXSX vs. BOSOX - Dividend Comparison

FLXSX has not paid dividends to shareholders, while BOSOX's dividend yield for the trailing twelve months is around 4.14%.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
BOSOX Boston Trust Small Cap Fund	4.14%	4.41%	6.52%	0.78%	5.09%	8.93%	2.56%	12.46%	16.19%	9.13%	3.14%	18.92%
FLXSX Fidelity Flex Small Cap Index Fund	0.00%	0.00%	1.36%	1.49%	1.26%	2.74%	1.06%	2.86%	2.31%	0.77%	0.00%	0.00%

Frequently Asked Questions

Can I hold both FLXSX and BOSOX in my portfolio?

FLXSX and BOSOX have a correlation of 0.80, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, FLXSX or BOSOX?

FLXSX has higher volatility (5.03%) compared to BOSOX (3.90%). In terms of maximum drawdown, FLXSX dropped -41.72% vs BOSOX's -51.32%.

Which has better risk-adjusted returns?

FLXSX currently has the higher Sharpe Ratio (2.08 vs 0.53), 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.