CPTNX vs. FUMBX

Last updated Apr 3, 2026

Compare and contrast key facts about American Century Government Bond Fund (CPTNX) and Fidelity Short-Term Treasury Bond Index Fund (FUMBX).

CPTNX is managed by American Century. It was launched on May 15, 1980. FUMBX is a passively managed fund by Fidelity that tracks the performance of the Bloomberg Barclays 1-5 Year U.S. Treasury Index. It was launched on Dec 20, 2005.

Performance

CPTNX vs. FUMBX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in American Century Government Bond Fund (CPTNX) and Fidelity Short-Term Treasury Bond Index Fund (FUMBX). The values are adjusted to include any dividend payments, if applicable.

CPTNX vs. FUMBX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
CPTNX American Century Government Bond Fund	-0.22%	7.26%	0.32%	3.51%	-13.10%	-1.24%	6.71%	6.16%	0.57%	0.10%
FUMBX Fidelity Short-Term Treasury Bond Index Fund	0.16%	5.83%	3.25%	4.47%	-5.84%	-1.38%	4.22%	4.19%	1.47%	-0.33%

Returns By Period

In the year-to-date period, CPTNX achieves a -0.22% return, which is significantly lower than FUMBX's 0.16% return.

CPTNX

• 1D: 0.00%
• 1M: -1.47%
• YTD: -0.22%
• 6M: 0.58%
• 1Y: 3.89%
• 3Y*: 2.58%
• 5Y*: -0.51%
• 10Y*: 0.89%

FUMBX

• 1D: 0.00%
• 1M: -0.41%
• YTD: 0.16%
• 6M: 1.12%
• 1Y: 3.92%
• 3Y*: 3.89%
• 5Y*: 1.36%
• 10Y*: —

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

CPTNX vs. FUMBX - Expense Ratio Comparison

CPTNX has a 0.47% expense ratio, which is higher than FUMBX's 0.03% expense ratio.

CPTNX

American Century Government Bond Fund

FUMBX

Fidelity Short-Term Treasury Bond Index Fund

Return for Risk

CPTNX vs. FUMBX — Risk / Return Rank

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

CPTNX

CPTNX Risk / Return Rank: 28
CPTNX Sharpe Ratio Rank: 27
CPTNX Sortino Ratio Rank: 25
CPTNX Omega Ratio Rank: 18
CPTNX Calmar Ratio Rank: 41
CPTNX Martin Ratio Rank: 26

FUMBX

FUMBX Risk / Return Rank: 83
FUMBX Sharpe Ratio Rank: 82
FUMBX Sortino Ratio Rank: 89
FUMBX Omega Ratio Rank: 82
FUMBX Calmar Ratio Rank: 86
FUMBX Martin Ratio Rank: 76

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.

CPTNX vs. FUMBX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for American Century Government Bond Fund (CPTNX) and Fidelity Short-Term Treasury Bond Index Fund (FUMBX). 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.

	CPTNX	FUMBX	Difference
Sharpe ratio Return per unit of total volatility	0.80	1.65	-0.85
Sortino ratio Return per unit of downside risk	1.16	2.61	-1.44
Omega ratio Gain probability vs. loss probability	1.14	1.35	-0.21
Calmar ratio Return relative to maximum drawdown	1.40	2.49	-1.09
Martin ratio Return relative to average drawdown	3.78	8.60	-4.82
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

CPTNX vs. FUMBX - Sharpe Ratio Comparison

The current CPTNX Sharpe Ratio is 0.80, which is lower than the FUMBX Sharpe Ratio of 1.65. The chart below compares the historical Sharpe Ratios of CPTNX and FUMBX, offering insights into how both investments have performed under varying market conditions. These values are calculated using daily returns over the previous 12 months.

Sharpe Ratios by Period

	CPTNX	FUMBX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	0.80	1.65	-0.85
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	-0.08	0.47	-0.55
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.18	—	—
Sharpe Ratio (All Time) Calculated using the full available price history	1.15	0.74	+0.41

Correlation

The correlation between CPTNX and FUMBX is 0.84, which is considered to be high. That indicates a strong positive relationship between their price movements. Having highly-correlated positions in a portfolio may signal a lack of diversification, potentially leading to increased risk during market downturns.

Dividends

CPTNX vs. FUMBX - Dividend Comparison

CPTNX's dividend yield for the trailing twelve months is around 3.72%, more than FUMBX's 3.67% yield.

	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
CPTNX American Century Government Bond Fund	3.72%	4.07%	4.22%	3.72%	1.84%	2.10%	2.09%	2.48%	2.49%	2.14%	2.28%	1.69%
FUMBX Fidelity Short-Term Treasury Bond Index Fund	3.67%	3.51%	2.91%	1.64%	0.86%	1.15%	1.41%	1.88%	1.64%	0.34%	0.00%	0.00%

Drawdowns

CPTNX vs. FUMBX - Drawdown Comparison

The maximum CPTNX drawdown since its inception was -19.73%, which is greater than FUMBX's maximum drawdown of -8.83%. Use the drawdown chart below to compare losses from any high point for CPTNX and FUMBX.

Drawdown Indicators

	CPTNX	FUMBX	Difference
Max Drawdown Largest peak-to-trough decline	-19.73%	-8.83%	-10.90%
Max Drawdown (1Y) Largest decline over 1 year	-2.95%	-1.54%	-1.41%
Max Drawdown (5Y) Largest decline over 5 years	-19.15%	-8.60%	-10.55%
Max Drawdown (10Y) Largest decline over 10 years	-19.73%	—	—
Current Drawdown Current decline from peak	-5.30%	-0.80%	-4.50%
Average Drawdown Average peak-to-trough decline	-2.28%	-1.88%	-0.40%
Ulcer Index Depth and duration of drawdowns from previous peaks	1.09%	0.44%	+0.65%

Volatility

CPTNX vs. FUMBX - Volatility Comparison

American Century Government Bond Fund (CPTNX) has a higher volatility of 1.59% compared to Fidelity Short-Term Treasury Bond Index Fund (FUMBX) at 0.83%. This indicates that CPTNX's price experiences larger fluctuations and is considered to be riskier than FUMBX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	CPTNX	FUMBX	Difference
Volatility (1M) Calculated over the trailing 1-month period	1.59%	0.83%	+0.76%
Volatility (6M) Calculated over the trailing 6-month period	2.65%	1.39%	+1.26%
Volatility (1Y) Calculated over the trailing 1-year period	4.60%	2.32%	+2.28%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	6.24%	2.89%	+3.35%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	4.96%	2.49%	+2.47%