VLGIX vs. PRGMX

Last updated Jun 4, 2026

VLGIX (Vanguard Long-Term Treasury Index Fund Institutional Shares) and PRGMX (T. Rowe Price GNMA Fund) are both Government Bonds funds. Over the past 10 years, VLGIX returned -1.03%/yr vs 1.31%/yr for PRGMX. A 0.67 correlation means they provide meaningful diversification when combined. VLGIX charges 0.05%/yr vs 0.58%/yr for PRGMX.

Performance

VLGIX vs. PRGMX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Vanguard Long-Term Treasury Index Fund Institutional Shares (VLGIX) and T. Rowe Price GNMA Fund (PRGMX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, VLGIX achieves a -0.22% return, which is significantly lower than PRGMX's 0.93% return. Over the past 10 years, VLGIX has underperformed PRGMX with an annualized return of -1.03%, while PRGMX has yielded a comparatively higher 1.31% annualized return.

VLGIX

• 1D: 0.17%
• 1M: 1.13%
• YTD: -0.22%
• 6M: -1.29%
• 1Y: 5.63%
• 3Y*: -0.45%
• 5Y*: -4.92%
• 10Y*: -1.03%

PRGMX

• 1D: 0.00%
• 1M: 0.56%
• YTD: 0.93%
• 6M: 1.33%
• 1Y: 7.89%
• 3Y*: 4.84%
• 5Y*: 0.69%
• 10Y*: 1.31%

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

VLGIX vs. PRGMX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
VLGIX Vanguard Long-Term Treasury Index Fund Institutional Shares	-0.22%	5.46%	-6.11%	3.67%	-29.45%	-5.06%	17.72%	14.31%	-1.59%	8.64%
PRGMX T. Rowe Price GNMA Fund	0.93%	8.72%	1.86%	5.62%	-11.45%	-2.18%	4.21%	5.18%	0.58%	1.23%

Correlation

The correlation between VLGIX and PRGMX is 0.81, 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	0.81
Correlation (3Y) Calculated over the trailing 3-year period	0.86
Correlation (5Y) Calculated over the trailing 5-year period	0.80
Correlation (10Y) Calculated over the trailing 10-year period	0.69
Correlation (All Time) Calculated using the full available price history since Nov 24, 2009	0.67

The correlation between VLGIX and PRGMX shifts across timeframes, from 0.67 (all time) to 0.86 (3 years), reflecting how their relationship changes across market environments.

Return for Risk

VLGIX vs. PRGMX — Risk / Return Rank

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

VLGIX

VLGIX Risk / Return Rank: 7
VLGIX Sharpe Ratio Rank: 7
VLGIX Sortino Ratio Rank: 7
VLGIX Omega Ratio Rank: 7
VLGIX Calmar Ratio Rank: 8
VLGIX Martin Ratio Rank: 7

PRGMX

PRGMX Risk / Return Rank: 44
PRGMX Sharpe Ratio Rank: 42
PRGMX Sortino Ratio Rank: 46
PRGMX Omega Ratio Rank: 43
PRGMX Calmar Ratio Rank: 48
PRGMX Martin Ratio Rank: 41

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.

VLGIX vs. PRGMX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Vanguard Long-Term Treasury Index Fund Institutional Shares (VLGIX) and T. Rowe Price GNMA Fund (PRGMX). 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.

	VLGIX	PRGMX	Difference
Sharpe ratio: Return per unit of total volatility	0.62	1.89	-1.27
Sortino ratio: Return per unit of downside risk	0.94	2.86	-1.92
Omega ratio: Gain probability vs. loss probability	1.11	1.36	-0.25
Calmar ratio: Return relative to maximum drawdown	0.79	2.64	-1.85
Martin ratio: Return relative to average drawdown	2.06	8.88	-6.82
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

VLGIX vs. PRGMX - Sharpe Ratio Comparison

The current VLGIX Sharpe Ratio is 0.62, which is lower than the PRGMX Sharpe Ratio of 1.89. The chart below compares the historical Sharpe Ratios of VLGIX and PRGMX, 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

	VLGIX	PRGMX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	0.62	1.89	-1.27
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	-0.34	0.11	-0.45
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	-0.08	0.28	-0.35
Sharpe Ratio (All Time) Calculated using the full available price history	0.19	0.93	-0.74

Drawdowns

VLGIX vs. PRGMX - Drawdown Comparison

The maximum VLGIX drawdown since its inception was -46.23%, which is greater than PRGMX's maximum drawdown of -18.22%. Use the drawdown chart below to compare losses from any high point for VLGIX and PRGMX.

Drawdown Indicators

	VLGIX	PRGMX	Difference
Max Drawdown Largest peak-to-trough decline	-46.23%	-18.22%	-28.01%
Max Drawdown (1Y) Largest decline over 1 year	-6.99%	-3.00%	-3.99%
Max Drawdown (3Y) Largest decline over 3 years	-17.65%	-7.14%	-10.51%
Max Drawdown (5Y) Largest decline over 5 years	-41.00%	-17.30%	-23.70%
Max Drawdown (10Y) Largest decline over 10 years	-46.23%	-18.22%	-28.01%
Current Drawdown Current decline from peak	-36.41%	-1.25%	-35.16%
Average Drawdown Average peak-to-trough decline	-15.03%	-2.24%	-12.79%
Ulcer Index Depth and duration of drawdowns from previous peaks	2.68%	0.89%	+1.79%

Volatility

VLGIX vs. PRGMX - Volatility Comparison

Vanguard Long-Term Treasury Index Fund Institutional Shares (VLGIX) has a higher volatility of 2.69% compared to T. Rowe Price GNMA Fund (PRGMX) at 1.72%. This indicates that VLGIX's price experiences larger fluctuations and is considered to be riskier than PRGMX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	VLGIX	PRGMX	Difference
Volatility (1M) Calculated over the trailing 1-month period	2.69%	1.72%	+0.97%
Volatility (6M) Calculated over the trailing 6-month period	6.07%	3.11%	+2.96%
Volatility (1Y) Calculated over the trailing 1-year period	8.98%	4.20%	+4.78%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	14.56%	6.38%	+8.18%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	13.72%	4.77%	+8.95%

VLGIX vs. PRGMX - Expense Ratio Comparison

VLGIX has a 0.05% expense ratio, which is lower than PRGMX's 0.58% expense ratio.

Dividends

VLGIX vs. PRGMX - Dividend Comparison

VLGIX's dividend yield for the trailing twelve months is around 4.59%, less than PRGMX's 4.99% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
PRGMX T. Rowe Price GNMA Fund	4.99%	4.96%	4.47%	3.54%	1.38%	0.59%	1.44%	2.39%	2.78%	2.98%	2.88%	3.12%
VLGIX Vanguard Long-Term Treasury Index Fund Institutional Shares	4.59%	4.43%	4.67%	3.31%	2.83%	1.78%	2.15%	2.46%	2.73%	2.57%	2.70%	2.82%

Frequently Asked Questions

Can I hold both VLGIX and PRGMX in my portfolio?

VLGIX and PRGMX have a correlation of 0.81, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, VLGIX or PRGMX?

VLGIX has higher volatility (2.69%) compared to PRGMX (1.72%). In terms of maximum drawdown, VLGIX dropped -46.23% vs PRGMX's -18.22%.

Which has better risk-adjusted returns?

PRGMX currently has the higher Sharpe Ratio (1.89 vs 0.62), 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.