ACBPX vs. SSAFX

Last updated Jun 6, 2026

ACBPX (American Century Diversified Bond Fund) and SSAFX (State Street Aggregate Bond Index Portfolio) are both Intermediate Core Bond funds. Over the past 10 years, ACBPX returned 1.40%/yr vs 27.83%/yr for SSAFX. Their correlation of 0.92 suggests significant overlap in exposure. ACBPX charges 0.39%/yr vs 0.02%/yr for SSAFX.

Performance

ACBPX vs. SSAFX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in American Century Diversified Bond Fund (ACBPX) and State Street Aggregate Bond Index Portfolio (SSAFX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, ACBPX achieves a 0.24% return, which is significantly lower than SSAFX's 0.34% return. Over the past 10 years, ACBPX has underperformed SSAFX with an annualized return of 1.40%, while SSAFX has yielded a comparatively higher 27.83% annualized return.

ACBPX

• 1D: 0.11%
• 1M: -0.18%
• YTD: 0.24%
• 6M: 0.63%
• 1Y: 5.10%
• 3Y*: 3.57%
• 5Y*: -0.34%
• 10Y*: 1.40%

SSAFX

• 1D: 0.12%
• 1M: -0.21%
• YTD: 0.34%
• 6M: 0.57%
• 1Y: 4.88%
• 3Y*: 3.87%
• 5Y*: -0.01%
• 10Y*: 27.83%

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

ACBPX vs. SSAFX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
ACBPX American Century Diversified Bond Fund	0.24%	7.42%	0.80%	4.66%	-14.28%	-0.65%	8.26%	8.59%	-1.25%	3.49%
SSAFX State Street Aggregate Bond Index Portfolio	0.34%	6.81%	1.34%	5.61%	-13.30%	-1.72%	978.57%	8.69%	-0.12%	3.38%

Correlation

The correlation between ACBPX and SSAFX is 0.91, 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	0.91
Correlation (3Y) Calculated over the trailing 3-year period	0.94
Correlation (5Y) Calculated over the trailing 5-year period	0.95
Correlation (10Y) Calculated over the trailing 10-year period	0.93
Correlation (All Time) Calculated using the full available price history since Sep 23, 2014	0.92

The correlation between ACBPX and SSAFX has been stable across timeframes, ranging from 0.91 to 0.95 - a consistent structural relationship.

Return for Risk

ACBPX vs. SSAFX — Risk / Return Rank

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

ACBPX

ACBPX Risk / Return Rank: 21
ACBPX Sharpe Ratio Rank: 20
ACBPX Sortino Ratio Rank: 21
ACBPX Omega Ratio Rank: 20
ACBPX Calmar Ratio Rank: 23
ACBPX Martin Ratio Rank: 20

SSAFX

SSAFX Risk / Return Rank: 22
SSAFX Sharpe Ratio Rank: 22
SSAFX Sortino Ratio Rank: 22
SSAFX Omega Ratio Rank: 20
SSAFX Calmar Ratio Rank: 24
SSAFX 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.

ACBPX vs. SSAFX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for American Century Diversified Bond Fund (ACBPX) and State Street Aggregate Bond Index Portfolio (SSAFX). 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.

	ACBPX	SSAFX	Difference
Sharpe ratio: Return per unit of total volatility	1.23	1.27	-0.04
Sortino ratio: Return per unit of downside risk	1.85	1.89	-0.04
Omega ratio: Gain probability vs. loss probability	1.22	1.22	0.00
Calmar ratio: Return relative to maximum drawdown	1.67	1.71	-0.04
Martin ratio: Return relative to average drawdown	4.91	5.18	-0.27
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

ACBPX vs. SSAFX - Sharpe Ratio Comparison

The current ACBPX Sharpe Ratio is 1.23, which is comparable to the SSAFX Sharpe Ratio of 1.27. The chart below compares the historical Sharpe Ratios of ACBPX and SSAFX, 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

	ACBPX	SSAFX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	1.23	1.27	-0.04
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	-0.05	-0.00	-0.05
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.28	0.10	+0.18
Sharpe Ratio (All Time) Calculated using the full available price history	0.57	0.09	+0.47

Drawdowns

ACBPX vs. SSAFX - Drawdown Comparison

The maximum ACBPX drawdown since its inception was -18.99%, roughly equal to the maximum SSAFX drawdown of -18.74%. Use the drawdown chart below to compare losses from any high point for ACBPX and SSAFX.

Drawdown Indicators

	ACBPX	SSAFX	Difference
Max Drawdown Largest peak-to-trough decline	-18.99%	-18.74%	-0.25%
Max Drawdown (1Y) Largest decline over 1 year	-2.93%	-2.74%	-0.19%
Max Drawdown (3Y) Largest decline over 3 years	-6.90%	-6.09%	-0.81%
Max Drawdown (5Y) Largest decline over 5 years	-18.99%	-18.10%	-0.89%
Max Drawdown (10Y) Largest decline over 10 years	-18.99%	-18.74%	-0.25%
Current Drawdown Current decline from peak	-3.66%	-2.69%	-0.97%
Average Drawdown Average peak-to-trough decline	-3.37%	-4.41%	+1.04%
Ulcer Index Depth and duration of drawdowns from previous peaks	0.99%	0.91%	+0.08%

Volatility

ACBPX vs. SSAFX - Volatility Comparison

American Century Diversified Bond Fund (ACBPX) has a higher volatility of 1.35% compared to State Street Aggregate Bond Index Portfolio (SSAFX) at 1.25%. This indicates that ACBPX's price experiences larger fluctuations and is considered to be riskier than SSAFX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	ACBPX	SSAFX	Difference
Volatility (1M) Calculated over the trailing 1-month period	1.35%	1.25%	+0.10%
Volatility (6M) Calculated over the trailing 6-month period	2.85%	2.63%	+0.22%
Volatility (1Y) Calculated over the trailing 1-year period	4.03%	3.74%	+0.29%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	6.14%	5.94%	+0.20%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	5.04%	277.40%	-272.36%

ACBPX vs. SSAFX - Expense Ratio Comparison

ACBPX has a 0.39% expense ratio, which is higher than SSAFX's 0.02% expense ratio.

Dividends

ACBPX vs. SSAFX - Dividend Comparison

ACBPX's dividend yield for the trailing twelve months is around 4.57%, more than SSAFX's 4.17% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
ACBPX American Century Diversified Bond Fund	4.57%	4.60%	3.89%	3.32%	2.07%	2.60%	4.57%	2.48%	2.83%	2.30%	2.63%	2.88%
SSAFX State Street Aggregate Bond Index Portfolio	4.17%	3.70%	3.76%	3.16%	2.49%	1.90%	2.41%	2.88%	2.82%	2.42%	2.21%	3.21%

Frequently Asked Questions

Can I hold both ACBPX and SSAFX in my portfolio?

With a correlation of 0.91, ACBPX and SSAFX 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, ACBPX or SSAFX?

ACBPX has higher volatility (1.35%) compared to SSAFX (1.25%). In terms of maximum drawdown, ACBPX dropped -18.99% vs SSAFX's -18.74%.

Which has better risk-adjusted returns?

SSAFX currently has the higher Sharpe Ratio (1.27 vs 1.23), 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.