REBYX vs. MOPIX

Last updated Jun 4, 2026

REBYX (Russell Investments U.S. Small Cap Equity Fund) and MOPIX (MainStay WMC Small Companies Fund) are both Small Cap Blend Equities funds. Over the past 10 years, REBYX returned 9.36%/yr vs 9.35%/yr for MOPIX. Their correlation of 0.95 suggests significant overlap in exposure. REBYX charges 0.90%/yr vs 0.97%/yr for MOPIX.

Performance

REBYX vs. MOPIX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Russell Investments U.S. Small Cap Equity Fund (REBYX) and MainStay WMC Small Companies Fund (MOPIX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, REBYX achieves a 17.23% return, which is significantly lower than MOPIX's 27.70% return. Both investments have delivered pretty close results over the past 10 years, with REBYX having a 9.36% annualized return and MOPIX not far behind at 9.35%.

REBYX

• 1D: 0.47%
• 1M: 4.17%
• YTD: 17.23%
• 6M: 16.82%
• 1Y: 36.24%
• 3Y*: 15.12%
• 5Y*: 6.27%
• 10Y*: 9.36%

MOPIX

• 1D: 0.76%
• 1M: 9.92%
• YTD: 27.70%
• 6M: 27.77%
• 1Y: 56.29%
• 3Y*: 23.19%
• 5Y*: 9.07%
• 10Y*: 9.35%

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

REBYX vs. MOPIX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
REBYX Russell Investments U.S. Small Cap Equity Fund	17.23%	8.86%	8.16%	13.81%	-16.14%	26.28%	13.04%	23.74%	-12.22%	2.12%
MOPIX MainStay WMC Small Companies Fund	27.70%	12.69%	16.07%	10.97%	-19.00%	17.55%	10.04%	17.70%	-16.42%	15.68%

Correlation

The correlation between REBYX and MOPIX is 0.94, 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	0.94
Correlation (3Y) Calculated over the trailing 3-year period	0.94
Correlation (5Y) Calculated over the trailing 5-year period	0.96
Correlation (10Y) Calculated over the trailing 10-year period	0.95
Correlation (All Time) Calculated using the full available price history since Jan 3, 2001	0.95

The correlation between REBYX and MOPIX has been stable across timeframes, ranging from 0.94 to 0.96 - a consistent structural relationship.

Return for Risk

REBYX vs. MOPIX — Risk / Return Rank

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

REBYX

REBYX Risk / Return Rank: 64
REBYX Sharpe Ratio Rank: 54
REBYX Sortino Ratio Rank: 54
REBYX Omega Ratio Rank: 47
REBYX Calmar Ratio Rank: 87
REBYX Martin Ratio Rank: 78

MOPIX

MOPIX Risk / Return Rank: 91
MOPIX Sharpe Ratio Rank: 93
MOPIX Sortino Ratio Rank: 89
MOPIX Omega Ratio Rank: 80
MOPIX Calmar Ratio Rank: 96
MOPIX Martin Ratio Rank: 95

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.

REBYX vs. MOPIX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Russell Investments U.S. Small Cap Equity Fund (REBYX) and MainStay WMC Small Companies Fund (MOPIX). 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.

	REBYX	MOPIX	Difference
Sharpe ratio Return per unit of total volatility	2.17	3.20	-1.03
Sortino ratio Return per unit of downside risk	3.09	4.37	-1.28
Omega ratio Gain probability vs. loss probability	1.37	1.53	-0.15
Calmar ratio Return relative to maximum drawdown	4.23	6.08	-1.84
Martin ratio Return relative to average drawdown	14.63	22.94	-8.30
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

REBYX vs. MOPIX - Sharpe Ratio Comparison

The current REBYX Sharpe Ratio is 2.17, which is lower than the MOPIX Sharpe Ratio of 3.20. The chart below compares the historical Sharpe Ratios of REBYX and MOPIX, 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

	REBYX	MOPIX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	2.17	3.20	-1.03
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.28	0.40	-0.12
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.40	0.40	0.00
Sharpe Ratio (All Time) Calculated using the full available price history	0.34	0.49	-0.15

Drawdowns

REBYX vs. MOPIX - Drawdown Comparison

The maximum REBYX drawdown since its inception was -62.03%, smaller than the maximum MOPIX drawdown of -68.08%. Use the drawdown chart below to compare losses from any high point for REBYX and MOPIX.

Drawdown Indicators

	REBYX	MOPIX	Difference
Max Drawdown Largest peak-to-trough decline	-62.03%	-68.08%	+6.05%
Max Drawdown (1Y) Largest decline over 1 year	-9.16%	-9.84%	+0.68%
Max Drawdown (3Y) Largest decline over 3 years	-32.68%	-26.99%	-5.69%
Max Drawdown (5Y) Largest decline over 5 years	-32.68%	-32.60%	-0.08%
Max Drawdown (10Y) Largest decline over 10 years	-44.79%	-48.01%	+3.22%
Current Drawdown Current decline from peak	-0.23%	0.00%	-0.23%
Average Drawdown Average peak-to-trough decline	-11.18%	-9.11%	-2.07%
Ulcer Index Depth and duration of drawdowns from previous peaks	2.65%	2.60%	+0.05%

Volatility

REBYX vs. MOPIX - Volatility Comparison

The current volatility for Russell Investments U.S. Small Cap Equity Fund (REBYX) is 5.06%, while MainStay WMC Small Companies Fund (MOPIX) has a volatility of 5.92%. This indicates that REBYX experiences smaller price fluctuations and is considered to be less risky than MOPIX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	REBYX	MOPIX	Difference
Volatility (1M) Calculated over the trailing 1-month period	5.06%	5.92%	-0.86%
Volatility (6M) Calculated over the trailing 6-month period	12.42%	13.71%	-1.29%
Volatility (1Y) Calculated over the trailing 1-year period	17.84%	18.68%	-0.84%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	22.76%	22.81%	-0.05%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	23.53%	23.38%	+0.15%

REBYX vs. MOPIX - Expense Ratio Comparison

REBYX has a 0.90% expense ratio, which is lower than MOPIX's 0.97% expense ratio.

Dividends

REBYX vs. MOPIX - Dividend Comparison

REBYX's dividend yield for the trailing twelve months is around 7.06%, more than MOPIX's 0.12% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
MOPIX MainStay WMC Small Companies Fund	0.12%	0.15%	0.39%	0.33%	2.34%	29.42%	0.00%	0.50%	18.09%	8.32%	0.59%	0.37%
REBYX Russell Investments U.S. Small Cap Equity Fund	7.06%	8.28%	13.03%	2.64%	5.30%	31.12%	0.64%	4.46%	18.61%	0.33%	0.88%	8.23%

Frequently Asked Questions

Can I hold both REBYX and MOPIX in my portfolio?

With a correlation of 0.94, REBYX and MOPIX move almost identically. Holding both adds very little diversification - you're essentially doubling your position in the same market segment. Choosing one is usually more capital-efficient.

Which is riskier, REBYX or MOPIX?

MOPIX has higher volatility (5.92%) compared to REBYX (5.06%). In terms of maximum drawdown, REBYX dropped -62.03% vs MOPIX's -68.08%.

Which has better risk-adjusted returns?

MOPIX currently has the higher Sharpe Ratio (3.20 vs 2.17), 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.