STMGX vs. BBMIX

Last updated Jul 14, 2026

STMGX (American Beacon Stephens Mid-Cap Growth Fund) and BBMIX (BBH Select Series - Mid Cap Fund) are both Mid Cap Growth Equities funds. Over the past 5 years, STMGX returned 5.88%/yr vs 2.22%/yr for BBMIX. Their correlation of 0.82 suggests significant overlap in exposure. STMGX charges 1.14%/yr vs 0.90%/yr for BBMIX.

Performance

STMGX vs. BBMIX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in American Beacon Stephens Mid-Cap Growth Fund (STMGX) and BBH Select Series - Mid Cap Fund (BBMIX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, STMGX achieves a 11.49% return, which is significantly higher than BBMIX's 2.86% return.

STMGX

• 1D: -0.77%
• 1M: 1.28%
• 6M: 6.34%
• YTD: 11.49%
• 1Y: 16.67%
• 3Y*: 15.08%
• 5Y*: 5.88%
• 10Y*: 13.52%

BBMIX

• 1D: 0.00%
• 1M: 0.00%
• 6M: 2.86%
• YTD: 2.86%
• 1Y: -3.85%
• 3Y*: 4.78%
• 5Y*: 2.22%
• 10Y*: —

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

STMGX vs. BBMIX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021
STMGX American Beacon Stephens Mid-Cap Growth Fund	11.49%	12.98%	13.16%	25.22%	-28.31%	11.43%
BBMIX BBH Select Series - Mid Cap Fund	2.86%	-6.45%	11.41%	26.01%	-24.76%	13.50%

Correlation

The correlation between STMGX and BBMIX is 0.42, which is low. Their price movements are largely independent, making them effective diversification partners.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.42
Correlation (3Y) Calculated over the trailing 3-year period	0.73
Correlation (5Y) Calculated over the trailing 5-year period	0.83
Correlation (All Time) Calculated using the full available price history since May 24, 2021	0.82

Over the past year, the correlation between STMGX and BBMIX has dropped to 0.42 - well below their long-term average of 0.82, suggesting their price drivers have been diverging.

Return for Risk

STMGX vs. BBMIX — Risk / Return Rank

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

STMGX

STMGX Risk / Return Rank: 22
STMGX Sharpe Ratio Rank: 19
STMGX Sortino Ratio Rank: 20
STMGX Omega Ratio Rank: 18
STMGX Calmar Ratio Rank: 27
STMGX Martin Ratio Rank: 29

BBMIX

BBMIX Risk / Return Rank: 1
BBMIX Sharpe Ratio Rank: 1
BBMIX Sortino Ratio Rank: 1
BBMIX Omega Ratio Rank: 1
BBMIX Calmar Ratio Rank: 1
BBMIX Martin Ratio Rank: 1

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.

STMGX vs. BBMIX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for American Beacon Stephens Mid-Cap Growth Fund (STMGX) and BBH Select Series - Mid Cap Fund (BBMIX). 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.

	STMGX	BBMIX	Difference
Sharpe ratio: Return per unit of total volatility	0.93	-0.54	+1.46
Sortino ratio: Return per unit of downside risk	1.39	-0.71	+2.10
Omega ratio: Gain probability vs. loss probability	1.16	0.89	+0.28
Calmar ratio: Return relative to maximum drawdown	1.47	-0.65	+2.12
Martin ratio: Return relative to average drawdown	5.10	-0.95	+6.05

STMGX vs. BBMIX - Sharpe Ratio Comparison

The current STMGX Sharpe Ratio is 0.93, which is higher than the BBMIX Sharpe Ratio of -0.54. The chart below compares the historical Sharpe Ratios of STMGX and BBMIX, 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

STMGX vs. BBMIX - Drawdown Comparison

The maximum STMGX drawdown since its inception was -57.58%, which is greater than BBMIX's maximum drawdown of -28.90%. Use the drawdown chart below to compare losses from any high point for STMGX and BBMIX.

Drawdown Indicators

	STMGX	BBMIX	Difference
Max Drawdown Largest peak-to-trough decline	-57.58%	-28.90%	-28.68%
Max Drawdown (1Y) Largest decline over 1 year	-10.84%	-8.89%	-1.95%
Max Drawdown (3Y) Largest decline over 3 years	-22.50%	-23.79%	+1.29%
Max Drawdown (5Y) Largest decline over 5 years	-36.59%	-28.90%	-7.69%
Max Drawdown (10Y) Largest decline over 10 years	-36.59%	—	—
Current Drawdown Current decline from peak	-1.96%	-11.28%	+9.32%
Average Drawdown Average peak-to-trough decline	-10.11%	-10.52%	+0.41%
Ulcer Index Depth and duration of drawdowns from previous peaks	3.12%	5.46%	-2.34%

Volatility

STMGX vs. BBMIX - Volatility Comparison

American Beacon Stephens Mid-Cap Growth Fund (STMGX) has a higher volatility of 5.80% compared to BBH Select Series - Mid Cap Fund (BBMIX) at 0.00%. This indicates that STMGX's price experiences larger fluctuations and is considered to be riskier than BBMIX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	STMGX	BBMIX	Difference
Volatility (1M) Calculated over the trailing 1-month period	5.80%	0.00%	+5.80%
Volatility (6M) Calculated over the trailing 6-month period	13.56%	4.71%	+8.85%
Volatility (1Y) Calculated over the trailing 1-year period	17.23%	10.72%	+6.51%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	20.99%	19.66%	+1.33%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	20.86%	19.47%	+1.39%

STMGX vs. BBMIX - Expense Ratio Comparison

STMGX has a 1.14% expense ratio, which is higher than BBMIX's 0.90% expense ratio.

Dividends

STMGX vs. BBMIX - Dividend Comparison

STMGX's dividend yield for the trailing twelve months is around 30.83%, while BBMIX has not paid dividends to shareholders.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
BBMIX BBH Select Series - Mid Cap Fund	0.00%	0.00%	0.32%	0.10%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%
STMGX American Beacon Stephens Mid-Cap Growth Fund	30.83%	34.38%	4.86%	0.00%	3.42%	7.49%	1.45%	3.60%	9.39%	5.40%	6.65%	5.62%

Frequently Asked Questions

Can I hold both STMGX and BBMIX in my portfolio?

STMGX and BBMIX have a correlation of 0.42, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, STMGX or BBMIX?

STMGX has higher volatility (5.80%) compared to BBMIX (0.00%). In terms of maximum drawdown, STMGX dropped -57.58% vs BBMIX's -28.90%.

Which has better risk-adjusted returns?

STMGX currently has the higher Sharpe Ratio (0.93 vs -0.54), 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.