ARMGX vs. PRTBX

Last updated Jun 5, 2026

ARMGX (Western Asset Ultra-Short Income Fund) and PRTBX (Permanent Portfolio Short-Term Treasury Portfolio) are both Ultrashort Bond funds. Over the past 10 years, ARMGX returned 2.24%/yr vs 1.26%/yr for PRTBX. At a 0.09 correlation, their price movements are largely independent. ARMGX charges 1.32%/yr vs 0.65%/yr for PRTBX.

Performance

ARMGX vs. PRTBX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Western Asset Ultra-Short Income Fund (ARMGX) and Permanent Portfolio Short-Term Treasury Portfolio (PRTBX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, ARMGX achieves a 1.18% return, which is significantly higher than PRTBX's 0.75% return. Over the past 10 years, ARMGX has outperformed PRTBX with an annualized return of 2.24%, while PRTBX has yielded a comparatively lower 1.26% annualized return.

ARMGX

• 1D: 0.00%
• 1M: 0.38%
• YTD: 1.18%
• 6M: 1.57%
• 1Y: 3.71%
• 3Y*: 4.42%
• 5Y*: 2.66%
• 10Y*: 2.24%

PRTBX

• 1D: -0.02%
• 1M: 0.15%
• YTD: 0.75%
• 6M: 1.02%
• 1Y: 3.05%
• 3Y*: 3.85%
• 5Y*: 1.98%
• 10Y*: 1.26%

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

ARMGX vs. PRTBX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
ARMGX Western Asset Ultra-Short Income Fund	1.18%	4.20%	4.67%	5.25%	-1.91%	0.06%	0.80%	3.38%	0.91%	3.09%
PRTBX Permanent Portfolio Short-Term Treasury Portfolio	0.75%	4.19%	4.12%	3.79%	-2.28%	-0.74%	0.10%	1.76%	1.16%	0.12%

Correlation

The correlation between ARMGX and PRTBX is 0.33, which is low. Their price movements are largely independent, making them effective diversification partners.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.33
Correlation (3Y) Calculated over the trailing 3-year period	0.36
Correlation (5Y) Calculated over the trailing 5-year period	0.27
Correlation (10Y) Calculated over the trailing 10-year period	0.18
Correlation (All Time) Calculated using the full available price history since Jun 21, 1996	0.09

Over the past year, ARMGX and PRTBX have become more correlated (0.33) than their long-term average of 0.09, meaning their price movements have been converging.

Return for Risk

ARMGX vs. PRTBX — Risk / Return Rank

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

ARMGX

ARMGX Risk / Return Rank: 98
ARMGX Sharpe Ratio Rank: 94
ARMGX Sortino Ratio Rank: 98
ARMGX Omega Ratio Rank: 99
ARMGX Calmar Ratio Rank: 99
ARMGX Martin Ratio Rank: 99

PRTBX

PRTBX Risk / Return Rank: 99
PRTBX Sharpe Ratio Rank: 99
PRTBX Sortino Ratio Rank: 99
PRTBX Omega Ratio Rank: 98
PRTBX Calmar Ratio Rank: 99
PRTBX Martin Ratio Rank: 99

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.

ARMGX vs. PRTBX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Western Asset Ultra-Short Income Fund (ARMGX) and Permanent Portfolio Short-Term Treasury Portfolio (PRTBX). 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.

	ARMGX	PRTBX	Difference
Sharpe ratio: Return per unit of total volatility	3.22	4.70	-1.48
Sortino ratio: Return per unit of downside risk	7.55	8.77	-1.21
Omega ratio: Gain probability vs. loss probability	2.64	2.25	+0.39
Calmar ratio: Return relative to maximum drawdown	11.77	9.97	+1.80
Martin ratio: Return relative to average drawdown	53.56	48.35	+5.21
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

ARMGX vs. PRTBX - Sharpe Ratio Comparison

The current ARMGX Sharpe Ratio is 3.22, which is lower than the PRTBX Sharpe Ratio of 4.70. The chart below compares the historical Sharpe Ratios of ARMGX and PRTBX, 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

	ARMGX	PRTBX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	3.22	4.70	-1.48
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	2.12	1.65	+0.48
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	1.39	1.46	-0.07
Sharpe Ratio (All Time) Calculated using the full available price history	1.12	3.89	-2.77

Drawdowns

ARMGX vs. PRTBX - Drawdown Comparison

The maximum ARMGX drawdown since its inception was -21.79%, which is greater than PRTBX's maximum drawdown of -5.13%. Use the drawdown chart below to compare losses from any high point for ARMGX and PRTBX.

Drawdown Indicators

	ARMGX	PRTBX	Difference
Max Drawdown Largest peak-to-trough decline	-21.79%	-5.13%	-16.66%
Max Drawdown (1Y) Largest decline over 1 year	-0.33%	-0.32%	-0.01%
Max Drawdown (3Y) Largest decline over 3 years	-0.55%	-0.44%	-0.11%
Max Drawdown (5Y) Largest decline over 5 years	-3.23%	-3.70%	+0.47%
Max Drawdown (10Y) Largest decline over 10 years	-9.09%	-4.36%	-4.73%
Current Drawdown Current decline from peak	0.00%	-0.03%	+0.03%
Average Drawdown Average peak-to-trough decline	-1.53%	-0.96%	-0.57%
Ulcer Index Depth and duration of drawdowns from previous peaks	0.07%	0.07%	0.00%

Volatility

ARMGX vs. PRTBX - Volatility Comparison

Western Asset Ultra-Short Income Fund (ARMGX) has a higher volatility of 0.40% compared to Permanent Portfolio Short-Term Treasury Portfolio (PRTBX) at 0.15%. This indicates that ARMGX's price experiences larger fluctuations and is considered to be riskier than PRTBX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	ARMGX	PRTBX	Difference
Volatility (1M) Calculated over the trailing 1-month period	0.40%	0.15%	+0.25%
Volatility (6M) Calculated over the trailing 6-month period	0.87%	0.40%	+0.47%
Volatility (1Y) Calculated over the trailing 1-year period	1.19%	0.68%	+0.51%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	1.26%	1.21%	+0.05%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	1.62%	0.86%	+0.76%

ARMGX vs. PRTBX - Expense Ratio Comparison

ARMGX has a 1.32% expense ratio, which is higher than PRTBX's 0.65% expense ratio.

Dividends

ARMGX vs. PRTBX - Dividend Comparison

ARMGX's dividend yield for the trailing twelve months is around 2.86%, less than PRTBX's 3.36% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
ARMGX Western Asset Ultra-Short Income Fund	2.86%	3.00%	2.43%	2.23%	1.37%	0.17%	1.45%	2.32%	1.92%	1.37%	0.96%	0.48%
PRTBX Permanent Portfolio Short-Term Treasury Portfolio	3.36%	3.39%	2.69%	1.79%	0.00%	0.00%	0.21%	1.65%	0.83%	0.00%	0.00%	0.00%

Frequently Asked Questions

Can I hold both ARMGX and PRTBX in my portfolio?

ARMGX and PRTBX have a correlation of 0.33, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, ARMGX or PRTBX?

ARMGX has higher volatility (0.40%) compared to PRTBX (0.15%). In terms of maximum drawdown, ARMGX dropped -21.79% vs PRTBX's -5.13%.

Which has better risk-adjusted returns?

PRTBX currently has the higher Sharpe Ratio (4.70 vs 3.22), 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.