OWMBX vs. FMBIX

Last updated Jun 3, 2026

OWMBX (Old Westbury Municipal Bond Fund) and FMBIX (Fidelity Municipal Bond Index Fund) are both Municipal Bonds funds. A 0.78 correlation means they provide meaningful diversification when combined. OWMBX charges 0.57%/yr vs 0.07%/yr for FMBIX.

Performance

OWMBX vs. FMBIX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Old Westbury Municipal Bond Fund (OWMBX) and Fidelity Municipal Bond Index Fund (FMBIX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

OWMBX

• 1D: 0.00%
• 1M: 0.17%
• YTD: 0.28%
• 6M: 0.67%
• 1Y: 4.37%
• 3Y*: 2.71%
• 5Y*: 0.62%
• 10Y*: 1.41%

FMBIX

• 1D: —
• 1M: —
• YTD: —
• 6M: —
• 1Y: —
• 3Y*: —
• 5Y*: —
• 10Y*: —

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

OWMBX vs. FMBIX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019
OWMBX Old Westbury Municipal Bond Fund	0.28%	4.29%	0.43%	4.03%	-5.39%	-0.63%	5.01%	1.25%
FMBIX Fidelity Municipal Bond Index Fund	0.00%	0.60%	1.32%	5.89%	-10.00%	1.14%	3.10%	1.48%

Correlation

The correlation between OWMBX and FMBIX is 0.78, which is moderate. They share some common price drivers but move independently often enough to provide real diversification benefit when combined.

	Correlation
Correlation (3Y) Calculated over the trailing 3-year period	0.71
Correlation (5Y) Calculated over the trailing 5-year period	0.79
Correlation (All Time) Calculated using the full available price history since Jul 18, 2019	0.78

The correlation between OWMBX and FMBIX has been stable across timeframes, ranging from 0.71 to 0.79 - a consistent structural relationship.

Return for Risk

OWMBX vs. FMBIX — Risk / Return Rank

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

OWMBX

OWMBX Risk / Return Rank: 62
OWMBX Sharpe Ratio Rank: 76
OWMBX Sortino Ratio Rank: 78
OWMBX Omega Ratio Rank: 92
OWMBX Calmar Ratio Rank: 36
OWMBX Martin Ratio Rank: 29

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.

OWMBX vs. FMBIX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Old Westbury Municipal Bond Fund (OWMBX) and Fidelity Municipal Bond Index Fund (FMBIX). 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.

	OWMBX	FMBIX	Difference
Sharpe ratio Return per unit of total volatility	2.53	—	—
Sortino ratio Return per unit of downside risk	3.72	—	—
Omega ratio Gain probability vs. loss probability	1.68	—	—
Calmar ratio Return relative to maximum drawdown	2.28	—	—
Martin ratio Return relative to average drawdown	6.97	—	—
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

Sharpe Ratios by Period

	OWMBX	FMBIX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	2.53	—	—
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.20	—	—
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.47	—	—
Sharpe Ratio (All Time) Calculated using the full available price history	1.05	—	—

Drawdowns

Drawdown Indicators

	OWMBX	FMBIX	Difference
Max Drawdown Largest peak-to-trough decline	-9.54%	—	—
Max Drawdown (1Y) Largest decline over 1 year	-2.45%	—	—
Max Drawdown (3Y) Largest decline over 3 years	-3.81%	—	—
Max Drawdown (5Y) Largest decline over 5 years	-9.37%	—	—
Max Drawdown (10Y) Largest decline over 10 years	-9.44%	—	—
Current Drawdown Current decline from peak	-1.33%	—	—
Average Drawdown Average peak-to-trough decline	-1.64%	—	—
Ulcer Index Depth and duration of drawdowns from previous peaks	0.80%	—	—

Volatility

Volatility by Period

	OWMBX	FMBIX	Difference
Volatility (1M) Calculated over the trailing 1-month period	0.64%	—	—
Volatility (6M) Calculated over the trailing 6-month period	1.44%	—	—
Volatility (1Y) Calculated over the trailing 1-year period	1.92%	—	—
Volatility (5Y) Calculated over the trailing 5-year period, annualized	3.11%	—	—
Volatility (10Y) Calculated over the trailing 10-year period, annualized	3.04%	—	—

OWMBX vs. FMBIX - Expense Ratio Comparison

OWMBX has a 0.57% expense ratio, which is higher than FMBIX's 0.07% expense ratio.

Dividends

OWMBX vs. FMBIX - Dividend Comparison

OWMBX's dividend yield for the trailing twelve months is around 2.61%, while FMBIX has not paid dividends to shareholders.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
FMBIX Fidelity Municipal Bond Index Fund	0.00%	0.70%	2.60%	2.29%	1.17%	1.28%	1.59%	0.77%	0.00%	0.00%	0.00%	0.00%
OWMBX Old Westbury Municipal Bond Fund	2.61%	2.61%	2.54%	2.01%	1.15%	2.06%	2.55%	1.68%	1.45%	1.18%	1.61%	1.40%

Frequently Asked Questions

Can I hold both OWMBX and FMBIX in my portfolio?

OWMBX and FMBIX have a correlation of 0.78, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.