STMGX vs. USMIX

Last updated Aug 1, 2026

STMGX (American Beacon Stephens Mid-Cap Growth Fund) and USMIX (USAA Extended Market Index Fund) are both Mid Cap Growth Equities funds. Over the past 10 years, STMGX returned 13.18%/yr vs 11.58%/yr for USMIX. Their correlation of 0.91 means they have usually moved in the same direction. STMGX charges 1.14%/yr vs 0.38%/yr for USMIX.

Performance

STMGX vs. USMIX - Performance Comparison

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

Returns By Period

In the year-to-date period, STMGX achieves a 9.34% return, which is significantly lower than USMIX's 14.54% return. Over the past 10 years, STMGX has outperformed USMIX with an annualized return of 13.18%, while USMIX has yielded a comparatively lower 11.58% annualized return.

STMGX

• 1D: 1.05%
• 1M: -2.98%
• 6M: 8.71%
• YTD: 9.34%
• 1Y: 12.54%
• 3Y*: 13.72%
• 5Y*: 5.02%
• 10Y*: 13.18%
• ALL TIME*: 9.76%

USMIX

• 1D: 0.74%
• 1M: -0.85%
• 6M: 10.00%
• YTD: 14.54%
• 1Y: 27.62%
• 3Y*: 14.44%
• 5Y*: 6.30%
• 10Y*: 11.58%
• ALL TIME*: 8.65%

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

Liquidity Comparison

Position	Avg. Volume Value (2W)	Avg. Volume Value (1M)	Avg. Volume Value (3M)
STMGX American Beacon Stephens Mid-Cap Growth Fund	$0.00	$0.00	$0.00
USMIX USAA Extended Market Index Fund	$0.00	$0.00	$0.00

STMGX vs. USMIX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
STMGX American Beacon Stephens Mid-Cap Growth Fund	9.34%	12.98%	13.16%	25.22%	-28.31%	12.29%	39.82%	31.31%	1.71%	27.97%
USMIX USAA Extended Market Index Fund	14.54%	10.44%	11.99%	25.81%	-24.04%	15.29%	31.20%	27.93%	-9.71%	17.72%

Correlation

The correlation between STMGX and USMIX is 0.86, meaning they have usually moved in the same direction, including during past declines.

	Correlation
Correlation (1Y) Focuses on recent behavior, but can change the most.	0.86
Correlation (3Y) Balances recent behavior with more history.	0.83
Correlation (5Y) Shows whether the relationship held over a longer period.	0.88
Correlation (10Y) Provides a long-term view across more market conditions.	0.87
Correlation (All Time) Calculated using the full available price history since Feb 2, 2006	0.91

The correlation between STMGX and USMIX has been stable across timeframes, ranging from 0.83 to 0.91 - a consistent structural relationship.

Return for Risk

STMGX vs. USMIX — Risk / Return Rank

Compare historical risk-adjusted metric ranks over the past 12 months.

STMGX

STMGX Risk / Return Rank: 16
STMGX Sharpe Ratio Rank: 13
STMGX Sortino Ratio Rank: 14
STMGX Omega Ratio Rank: 13
STMGX Calmar Ratio Rank: 17
STMGX Martin Ratio Rank: 21

USMIX

USMIX Risk / Return Rank: 66
USMIX Sharpe Ratio Rank: 61
USMIX Sortino Ratio Rank: 63
USMIX Omega Ratio Rank: 55
USMIX Calmar Ratio Rank: 76
USMIX Martin Ratio Rank: 74

The rank (0–100) uses a weighted average of the Sharpe, Sortino, Omega, Calmar, and Martin percentile ranks for the trailing 12 months. Higher means stronger historical risk-adjusted performance within the peer group.

STMGX vs. USMIX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for American Beacon Stephens Mid-Cap Growth Fund (STMGX) and USAA Extended Market Index Fund (USMIX). 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	USMIX	Difference
Sharpe ratio: Return per unit of total volatility	0.57	1.48	-0.91
Sortino ratio: Return per unit of downside risk	0.92	2.19	-1.27
Omega ratio: Gain probability vs. loss probability	1.11	1.26	-0.15
Calmar ratio: Return relative to maximum drawdown	0.91	2.47	-1.56
Martin ratio: Return relative to average drawdown	3.04	9.02	-5.98

STMGX vs. USMIX - Sharpe Ratio Comparison

The current STMGX Sharpe Ratio is 0.57, which is lower than the USMIX Sharpe Ratio of 1.48. The chart below compares the historical Sharpe Ratios of STMGX and USMIX, 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. USMIX - Drawdown Comparison

The maximum STMGX drawdown since its inception was -57.58%, roughly equal to the maximum USMIX drawdown of -57.91%. Use the drawdown chart below to compare losses from any high point for STMGX and USMIX.

Drawdown Indicators

	STMGX	USMIX	Difference
Max Drawdown Largest peak-to-trough decline	-57.58%	-57.91%	+0.33%
Max Drawdown (1Y) Largest decline over 1 year	-10.84%	-9.97%	-0.87%
Max Drawdown (3Y) Largest decline over 3 years	-22.50%	-31.84%	+9.34%
Max Drawdown (5Y) Largest decline over 5 years	-36.59%	-37.86%	+1.27%
Max Drawdown (10Y) Largest decline over 10 years	-36.59%	-41.86%	+5.27%
Current Drawdown Current decline from peak	-3.85%	-1.33%	-2.52%
Average Drawdown Average peak-to-trough decline	-10.09%	-11.93%	+1.84%
Ulcer Index Depth and duration of drawdowns from previous peaks	3.23%	2.73%	+0.50%

Volatility

STMGX vs. USMIX - Volatility Comparison

American Beacon Stephens Mid-Cap Growth Fund (STMGX) has a higher volatility of 3.75% compared to USAA Extended Market Index Fund (USMIX) at 3.25%. This indicates that STMGX's price experiences larger fluctuations and is considered to be riskier than USMIX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	STMGX	USMIX	Difference
Volatility (1M) Calculated over the trailing 1-month period	3.75%	3.25%	+0.50%
Volatility (6M) Calculated over the trailing 6-month period	13.57%	11.77%	+1.80%
Volatility (1Y) Calculated over the trailing 1-year period	17.27%	16.60%	+0.67%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	20.98%	24.94%	-3.96%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	20.87%	23.62%	-2.75%

STMGX vs. USMIX - Expense Ratio Comparison

STMGX has a 1.14% expense ratio, which is higher than USMIX's 0.38% expense ratio.

Dividends

STMGX vs. USMIX - Dividend Comparison

STMGX's dividend yield for the trailing twelve months is around 31.44%, more than USMIX's 5.65% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
STMGX American Beacon Stephens Mid-Cap Growth Fund	31.44%	34.38%	4.86%	0.00%	3.42%	7.49%	1.45%	3.60%	9.39%	5.40%	6.65%	5.62%
USMIX USAA Extended Market Index Fund	5.65%	6.47%	14.41%	4.41%	8.78%	17.98%	3.32%	3.18%	6.48%	7.48%	7.07%	8.02%

Frequently Asked Questions

Can I hold both STMGX and USMIX in my portfolio?

STMGX and USMIX have a correlation of 0.86, 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 USMIX?

STMGX has higher volatility (3.75%) compared to USMIX (3.25%). In terms of maximum drawdown, STMGX dropped -57.58% vs USMIX's -57.91%.

Which has better risk-adjusted returns?

USMIX currently has the higher Sharpe Ratio (1.48 vs 0.57), 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.