AHMFX vs. RFNBX

Last updated Jun 5, 2026

AHMFX (American High-Income Municipal Bond Fund Class F-2) and RFNBX (American Funds Fundamental Investors Fund Class R2) are both mutual funds - AHMFX is a High Yield Muni fund actively managed by Capital Group, while RFNBX is a Large Cap Blend Equities fund actively managed by Capital Group. Both are actively managed. Over the past 10 years, AHMFX returned 3.48%/yr vs 13.77%/yr for RFNBX. At a correlation of -0.08, they often move in opposite directions. AHMFX charges 0.42%/yr vs 1.36%/yr for RFNBX.

Performance

AHMFX vs. RFNBX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in American High-Income Municipal Bond Fund Class F-2 (AHMFX) and American Funds Fundamental Investors Fund Class R2 (RFNBX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, AHMFX achieves a 2.26% return, which is significantly lower than RFNBX's 13.96% return. Over the past 10 years, AHMFX has underperformed RFNBX with an annualized return of 3.48%, while RFNBX has yielded a comparatively higher 13.77% annualized return.

AHMFX

• 1D: -0.06%
• 1M: 0.86%
• YTD: 2.26%
• 6M: 2.77%
• 1Y: 8.28%
• 3Y*: 6.37%
• 5Y*: 1.87%
• 10Y*: 3.48%

RFNBX

• 1D: -0.70%
• 1M: 4.19%
• YTD: 13.96%
• 6M: 14.89%
• 1Y: 32.28%
• 3Y*: 24.82%
• 5Y*: 13.67%
• 10Y*: 13.77%

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

AHMFX vs. RFNBX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
AHMFX American High-Income Municipal Bond Fund Class F-2	2.26%	6.03%	6.45%	7.04%	-12.44%	5.49%	4.61%	9.12%	1.80%	9.09%
RFNBX American Funds Fundamental Investors Fund Class R2	13.96%	23.22%	21.80%	24.89%	-17.32%	21.49%	12.51%	26.09%	-8.89%	21.82%

Correlation

The correlation between AHMFX and RFNBX is 0.15, which is low. Their price movements are largely independent, making them effective diversification partners.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.15
Correlation (3Y) Calculated over the trailing 3-year period	0.14
Correlation (5Y) Calculated over the trailing 5-year period	0.11
Correlation (10Y) Calculated over the trailing 10-year period	0.03
Correlation (All Time) Calculated using the full available price history since Jan 5, 2009	-0.08

The correlation between AHMFX and RFNBX shifts across timeframes, from -0.08 (all time) to 0.15 (1 year), reflecting how their relationship changes across market environments.

Return for Risk

AHMFX vs. RFNBX — Risk / Return Rank

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

AHMFX

AHMFX Risk / Return Rank: 79
AHMFX Sharpe Ratio Rank: 87
AHMFX Sortino Ratio Rank: 92
AHMFX Omega Ratio Rank: 92
AHMFX Calmar Ratio Rank: 68
AHMFX Martin Ratio Rank: 57

RFNBX

RFNBX Risk / Return Rank: 67
RFNBX Sharpe Ratio Rank: 69
RFNBX Sortino Ratio Rank: 62
RFNBX Omega Ratio Rank: 63
RFNBX Calmar Ratio Rank: 66
RFNBX Martin Ratio Rank: 76

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.

AHMFX vs. RFNBX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for American High-Income Municipal Bond Fund Class F-2 (AHMFX) and American Funds Fundamental Investors Fund Class R2 (RFNBX). 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.

	AHMFX	RFNBX	Difference
Sharpe ratio: Return per unit of total volatility	2.82	2.38	+0.45
Sortino ratio: Return per unit of downside risk	4.63	3.22	+1.41
Omega ratio: Gain probability vs. loss probability	1.69	1.43	+0.26
Calmar ratio: Return relative to maximum drawdown	3.12	3.04	+0.08
Martin ratio: Return relative to average drawdown	11.17	13.98	-2.81
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

AHMFX vs. RFNBX - Sharpe Ratio Comparison

The current AHMFX Sharpe Ratio is 2.82, which is comparable to the RFNBX Sharpe Ratio of 2.38. The chart below compares the historical Sharpe Ratios of AHMFX and RFNBX, 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

	AHMFX	RFNBX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	2.82	2.38	+0.45
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.39	0.82	-0.43
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.77	0.78	-0.01
Sharpe Ratio (All Time) Calculated using the full available price history	1.54	0.60	+0.94

Drawdowns

AHMFX vs. RFNBX - Drawdown Comparison

The maximum AHMFX drawdown since its inception was -17.65%, smaller than the maximum RFNBX drawdown of -53.81%. Use the drawdown chart below to compare losses from any high point for AHMFX and RFNBX.

Drawdown Indicators

	AHMFX	RFNBX	Difference
Max Drawdown Largest peak-to-trough decline	-17.65%	-53.81%	+36.16%
Max Drawdown (1Y) Largest decline over 1 year	-2.76%	-10.78%	+8.02%
Max Drawdown (3Y) Largest decline over 3 years	-6.20%	-18.11%	+11.91%
Max Drawdown (5Y) Largest decline over 5 years	-17.65%	-25.53%	+7.88%
Max Drawdown (10Y) Largest decline over 10 years	-17.65%	-33.96%	+16.31%
Current Drawdown Current decline from peak	-0.06%	-0.70%	+0.64%
Average Drawdown Average peak-to-trough decline	-2.37%	-7.24%	+4.87%
Ulcer Index Depth and duration of drawdowns from previous peaks	0.77%	2.34%	-1.57%

Volatility

AHMFX vs. RFNBX - Volatility Comparison

The current volatility for American High-Income Municipal Bond Fund Class F-2 (AHMFX) is 1.10%, while American Funds Fundamental Investors Fund Class R2 (RFNBX) has a volatility of 3.82%. This indicates that AHMFX experiences smaller price fluctuations and is considered to be less risky than RFNBX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	AHMFX	RFNBX	Difference
Volatility (1M) Calculated over the trailing 1-month period	1.10%	3.82%	-2.72%
Volatility (6M) Calculated over the trailing 6-month period	2.21%	10.79%	-8.58%
Volatility (1Y) Calculated over the trailing 1-year period	3.05%	13.76%	-10.71%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	4.86%	16.80%	-11.94%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	4.55%	17.74%	-13.19%

AHMFX vs. RFNBX - Expense Ratio Comparison

AHMFX has a 0.42% expense ratio, which is lower than RFNBX's 1.36% expense ratio.

Dividends

AHMFX vs. RFNBX - Dividend Comparison

AHMFX's dividend yield for the trailing twelve months is around 4.12%, less than RFNBX's 6.92% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
AHMFX American High-Income Municipal Bond Fund Class F-2	4.12%	5.58%	4.04%	2.97%	2.71%	3.44%	3.60%	3.68%	3.88%	4.19%	3.74%	4.19%
RFNBX American Funds Fundamental Investors Fund Class R2	6.92%	7.90%	8.19%	5.13%	4.16%	10.27%	0.83%	6.20%	8.38%	6.54%	3.99%	5.32%

Frequently Asked Questions

Can I hold both AHMFX and RFNBX in my portfolio?

AHMFX and RFNBX have a correlation of 0.15, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, AHMFX or RFNBX?

RFNBX has higher volatility (3.82%) compared to AHMFX (1.10%). In terms of maximum drawdown, AHMFX dropped -17.65% vs RFNBX's -53.81%.

Which has better risk-adjusted returns?

AHMFX currently has the higher Sharpe Ratio (2.82 vs 2.38), 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.