CPTNX vs. FGMNX

Last updated Jun 5, 2026

CPTNX (American Century Government Bond Fund) and FGMNX (Fidelity GNMA Fund) are both Government Bonds funds. Over the past 10 years, CPTNX returned 0.84%/yr vs 1.21%/yr for FGMNX. A 0.78 correlation means they provide meaningful diversification when combined. CPTNX charges 0.47%/yr vs 0.45%/yr for FGMNX.

Performance

CPTNX vs. FGMNX - Performance Comparison

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

Returns By Period

In the year-to-date period, CPTNX achieves a -0.11% return, which is significantly lower than FGMNX's 0.89% return. Over the past 10 years, CPTNX has underperformed FGMNX with an annualized return of 0.84%, while FGMNX has yielded a comparatively higher 1.21% annualized return.

CPTNX

• 1D: -0.21%
• 1M: 0.01%
• YTD: -0.11%
• 6M: 0.12%
• 1Y: 4.28%
• 3Y*: 3.09%
• 5Y*: -0.63%
• 10Y*: 0.84%

FGMNX

• 1D: -0.19%
• 1M: 0.02%
• YTD: 0.89%
• 6M: 1.18%
• 1Y: 5.84%
• 3Y*: 4.19%
• 5Y*: 0.26%
• 10Y*: 1.21%

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

CPTNX vs. FGMNX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
CPTNX American Century Government Bond Fund	-0.11%	7.26%	0.32%	3.51%	-13.10%	-1.24%	6.71%	6.16%	0.57%	2.15%
FGMNX Fidelity GNMA Fund	0.89%	7.89%	0.43%	5.46%	-11.52%	-1.03%	3.74%	5.72%	0.62%	1.74%

Correlation

The correlation between CPTNX and FGMNX is 0.95 - these two move nearly in lockstep. At this level, holding both provides almost no diversification benefit. If you already own one, adding the other does little to reduce portfolio risk.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.95
Correlation (3Y) Calculated over the trailing 3-year period	0.95
Correlation (5Y) Calculated over the trailing 5-year period	0.94
Correlation (10Y) Calculated over the trailing 10-year period	0.88
Correlation (All Time) Calculated using the full available price history since Nov 11, 1985	0.78

The correlation between CPTNX and FGMNX shifts across timeframes, from 0.78 (all time) to 0.95 (1 year), reflecting how their relationship changes across market environments.

Return for Risk

CPTNX vs. FGMNX — Risk / Return Rank

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

CPTNX

CPTNX Risk / Return Rank: 18
CPTNX Sharpe Ratio Rank: 19
CPTNX Sortino Ratio Rank: 20
CPTNX Omega Ratio Rank: 18
CPTNX Calmar Ratio Rank: 18
CPTNX Martin Ratio Rank: 18

FGMNX

FGMNX Risk / Return Rank: 38
FGMNX Sharpe Ratio Rank: 36
FGMNX Sortino Ratio Rank: 38
FGMNX Omega Ratio Rank: 35
FGMNX Calmar Ratio Rank: 46
FGMNX Martin Ratio Rank: 38

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. FGMNX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for American Century Government Bond Fund (CPTNX) and Fidelity GNMA Fund (FGMNX). 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	FGMNX	Difference
Sharpe ratio: Return per unit of total volatility	1.22	1.71	-0.49
Sortino ratio: Return per unit of downside risk	1.84	2.59	-0.75
Omega ratio: Gain probability vs. loss probability	1.22	1.31	-0.10
Calmar ratio: Return relative to maximum drawdown	1.48	2.56	-1.07
Martin ratio: Return relative to average drawdown	4.69	8.21	-3.52
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. FGMNX - Sharpe Ratio Comparison

The current CPTNX Sharpe Ratio is 1.22, which is comparable to the FGMNX Sharpe Ratio of 1.71. The chart below compares the historical Sharpe Ratios of CPTNX and FGMNX, 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

	CPTNX	FGMNX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	1.22	1.71	-0.49
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	-0.10	0.04	-0.14
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.17	0.26	-0.09
Sharpe Ratio (All Time) Calculated using the full available price history	1.15	1.04	+0.11

Drawdowns

CPTNX vs. FGMNX - Drawdown Comparison

The maximum CPTNX drawdown since its inception was -19.73%, which is greater than FGMNX's maximum drawdown of -16.84%. Use the drawdown chart below to compare losses from any high point for CPTNX and FGMNX.

Drawdown Indicators

	CPTNX	FGMNX	Difference
Max Drawdown Largest peak-to-trough decline	-19.73%	-16.84%	-2.89%
Max Drawdown (1Y) Largest decline over 1 year	-3.36%	-2.54%	-0.82%
Max Drawdown (3Y) Largest decline over 3 years	-7.26%	-7.23%	-0.03%
Max Drawdown (5Y) Largest decline over 5 years	-19.15%	-16.54%	-2.61%
Max Drawdown (10Y) Largest decline over 10 years	-19.73%	-16.84%	-2.89%
Current Drawdown Current decline from peak	-5.20%	-1.28%	-3.92%
Average Drawdown Average peak-to-trough decline	-2.29%	-1.91%	-0.38%
Ulcer Index Depth and duration of drawdowns from previous peaks	1.06%	0.79%	+0.27%

Volatility

CPTNX vs. FGMNX - Volatility Comparison

American Century Government Bond Fund (CPTNX) has a higher volatility of 1.48% compared to Fidelity GNMA Fund (FGMNX) at 1.31%. This indicates that CPTNX's price experiences larger fluctuations and is considered to be riskier than FGMNX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	CPTNX	FGMNX	Difference
Volatility (1M) Calculated over the trailing 1-month period	1.48%	1.31%	+0.17%
Volatility (6M) Calculated over the trailing 6-month period	2.92%	2.66%	+0.26%
Volatility (1Y) Calculated over the trailing 1-year period	4.09%	3.81%	+0.28%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	6.29%	6.25%	+0.04%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	4.98%	4.67%	+0.31%

CPTNX vs. FGMNX - Expense Ratio Comparison

CPTNX has a 0.47% expense ratio, which is higher than FGMNX's 0.45% expense ratio.

Dividends

CPTNX vs. FGMNX - Dividend Comparison

CPTNX's dividend yield for the trailing twelve months is around 4.02%, more than FGMNX's 3.62% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
CPTNX American Century Government Bond Fund	4.02%	4.07%	4.22%	3.72%	1.84%	2.10%	2.09%	2.48%	2.49%	2.14%	2.28%	1.69%
FGMNX Fidelity GNMA Fund	3.62%	3.61%	3.23%	3.45%	1.68%	0.76%	1.61%	2.46%	2.19%	2.17%	2.61%	2.25%

Frequently Asked Questions

Can I hold both CPTNX and FGMNX in my portfolio?

With a correlation of 0.95, CPTNX and FGMNX 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, CPTNX or FGMNX?

CPTNX has higher volatility (1.48%) compared to FGMNX (1.31%). In terms of maximum drawdown, CPTNX dropped -19.73% vs FGMNX's -16.84%.

Which has better risk-adjusted returns?

FGMNX currently has the higher Sharpe Ratio (1.71 vs 1.22), 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.