TWUIX vs. MRFOX

Last updated Jul 25, 2026

TWUIX (American Century Ultra Fund I Class) and MRFOX (Marshfield Concentrated Opportunity Fund) are both Large Cap Growth Equities funds. Over the past 10 years, TWUIX returned 17.10%/yr vs 15.70%/yr for MRFOX. A 0.62 correlation means they provide meaningful diversification when combined. TWUIX charges 0.67%/yr vs 1.05%/yr for MRFOX.

Performance

TWUIX vs. MRFOX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in American Century Ultra Fund I Class (TWUIX) and Marshfield Concentrated Opportunity Fund (MRFOX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, TWUIX achieves a 0.54% return, which is significantly lower than MRFOX's 2.86% return. Over the past 10 years, TWUIX has outperformed MRFOX with an annualized return of 17.10%, while MRFOX has yielded a comparatively lower 15.70% annualized return.

TWUIX

• 1D: -2.19%
• 1M: -1.08%
• 6M: 0.81%
• YTD: 0.54%
• 1Y: 8.96%
• 3Y*: 16.60%
• 5Y*: 8.30%
• 10Y*: 17.10%
• ALL TIME*: 9.87%

MRFOX

• 1D: -0.62%
• 1M: 0.80%
• 6M: 0.63%
• YTD: 2.86%
• 1Y: 7.91%
• 3Y*: 12.49%
• 5Y*: 11.03%
• 10Y*: 15.70%
• ALL TIME*: 15.40%

*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)
MRFOX Marshfield Concentrated Opportunity Fund	$0.00	$0.00	$0.00
TWUIX American Century Ultra Fund I Class	$0.00	$0.00	$0.00

TWUIX vs. MRFOX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
TWUIX American Century Ultra Fund I Class	0.54%	12.88%	29.80%	43.63%	-32.25%	23.70%	50.09%	34.90%	0.90%	31.63%
MRFOX Marshfield Concentrated Opportunity Fund	2.86%	10.05%	17.10%	17.68%	5.06%	17.71%	15.19%	36.26%	1.89%	25.92%

Correlation

The correlation between TWUIX and MRFOX is 0.14, which is low. Their price movements are largely independent, making them effective diversification partners.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.14
Correlation (3Y) Calculated over the trailing 3-year period	0.35
Correlation (5Y) Calculated over the trailing 5-year period	0.53
Correlation (10Y) Calculated over the trailing 10-year period	0.61
Correlation (All Time) Calculated using the full available price history since Jan 4, 2016	0.62

Over the past year, the correlation between TWUIX and MRFOX has dropped to 0.14 - well below their long-term average of 0.62, suggesting their price drivers have been diverging.

Return for Risk

TWUIX vs. MRFOX — Risk / Return Rank

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

TWUIX

TWUIX Risk / Return Rank: 13
TWUIX Sharpe Ratio Rank: 13
TWUIX Sortino Ratio Rank: 13
TWUIX Omega Ratio Rank: 13
TWUIX Calmar Ratio Rank: 12
TWUIX Martin Ratio Rank: 13

MRFOX

MRFOX Risk / Return Rank: 21
MRFOX Sharpe Ratio Rank: 20
MRFOX Sortino Ratio Rank: 21
MRFOX Omega Ratio Rank: 19
MRFOX Calmar Ratio Rank: 23
MRFOX Martin Ratio Rank: 22

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.

TWUIX vs. MRFOX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for American Century Ultra Fund I Class (TWUIX) and Marshfield Concentrated Opportunity Fund (MRFOX). 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.

	TWUIX	MRFOX	Difference
Sharpe ratio: Return per unit of total volatility	0.50	0.80	-0.30
Sortino ratio: Return per unit of downside risk	0.80	1.26	-0.46
Omega ratio: Gain probability vs. loss probability	1.10	1.14	-0.05
Calmar ratio: Return relative to maximum drawdown	0.57	1.16	-0.58
Martin ratio: Return relative to average drawdown	1.82	3.40	-1.58

TWUIX vs. MRFOX - Sharpe Ratio Comparison

The current TWUIX Sharpe Ratio is 0.50, which is lower than the MRFOX Sharpe Ratio of 0.80. The chart below compares the historical Sharpe Ratios of TWUIX and MRFOX, 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

TWUIX vs. MRFOX - Drawdown Comparison

The maximum TWUIX drawdown since its inception was -61.41%, which is greater than MRFOX's maximum drawdown of -29.10%. Use the drawdown chart below to compare losses from any high point for TWUIX and MRFOX.

Drawdown Indicators

	TWUIX	MRFOX	Difference
Max Drawdown Largest peak-to-trough decline	-61.41%	-29.10%	-32.31%
Max Drawdown (1Y) Largest decline over 1 year	-15.64%	-7.03%	-8.61%
Max Drawdown (3Y) Largest decline over 3 years	-24.82%	-7.91%	-16.91%
Max Drawdown (5Y) Largest decline over 5 years	-35.12%	-12.98%	-22.14%
Max Drawdown (10Y) Largest decline over 10 years	-35.12%	-29.10%	-6.02%
Current Drawdown Current decline from peak	-8.76%	-2.41%	-6.35%
Average Drawdown Average peak-to-trough decline	-18.08%	-2.35%	-15.73%
Ulcer Index Depth and duration of drawdowns from previous peaks	4.93%	2.39%	+2.54%

Volatility

TWUIX vs. MRFOX - Volatility Comparison

American Century Ultra Fund I Class (TWUIX) has a higher volatility of 5.49% compared to Marshfield Concentrated Opportunity Fund (MRFOX) at 4.18%. This indicates that TWUIX's price experiences larger fluctuations and is considered to be riskier than MRFOX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	TWUIX	MRFOX	Difference
Volatility (1M) Calculated over the trailing 1-month period	5.49%	4.18%	+1.31%
Volatility (6M) Calculated over the trailing 6-month period	14.04%	7.66%	+6.38%
Volatility (1Y) Calculated over the trailing 1-year period	17.89%	10.18%	+7.71%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	22.78%	12.13%	+10.65%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	22.15%	14.17%	+7.98%

TWUIX vs. MRFOX - Expense Ratio Comparison

TWUIX has a 0.67% expense ratio, which is lower than MRFOX's 1.05% expense ratio.

Dividends

TWUIX vs. MRFOX - Dividend Comparison

TWUIX's dividend yield for the trailing twelve months is around 10.70%, more than MRFOX's 1.57% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
MRFOX Marshfield Concentrated Opportunity Fund	1.57%	1.62%	4.59%	0.46%	0.35%	6.78%	2.68%	1.39%	1.94%	2.06%	0.60%	0.00%
TWUIX American Century Ultra Fund I Class	10.70%	10.76%	3.36%	5.73%	7.03%	6.46%	2.68%	4.10%	7.94%	5.66%	4.44%	5.06%

Frequently Asked Questions

Can I hold both TWUIX and MRFOX in my portfolio?

TWUIX and MRFOX have a correlation of 0.14, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, TWUIX or MRFOX?

TWUIX has higher volatility (5.49%) compared to MRFOX (4.18%). In terms of maximum drawdown, TWUIX dropped -61.41% vs MRFOX's -29.10%.

Which has better risk-adjusted returns?

MRFOX currently has the higher Sharpe Ratio (0.80 vs 0.50), 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.