ACSNX vs. VBISX

Last updated Jun 4, 2026

ACSNX (American Century Short Duration Fund) and VBISX (Vanguard Short-Term Bond Index Fund) are both Short-Term Bond funds. Over the past 10 years, ACSNX returned 2.32%/yr vs 1.79%/yr for VBISX. A 0.72 correlation means they provide meaningful diversification when combined. ACSNX charges 0.57%/yr vs 0.15%/yr for VBISX.

Performance

ACSNX vs. VBISX - Performance Comparison

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

Returns By Period

In the year-to-date period, ACSNX achieves a 0.86% return, which is significantly higher than VBISX's 0.26% return. Over the past 10 years, ACSNX has outperformed VBISX with an annualized return of 2.32%, while VBISX has yielded a comparatively lower 1.79% annualized return.

ACSNX

• 1D: 0.00%
• 1M: 0.24%
• YTD: 0.86%
• 6M: 1.23%
• 1Y: 4.24%
• 3Y*: 4.85%
• 5Y*: 2.19%
• 10Y*: 2.32%

VBISX

• 1D: 0.00%
• 1M: 0.14%
• YTD: 0.26%
• 6M: 0.50%
• 1Y: 3.64%
• 3Y*: 4.14%
• 5Y*: 1.44%
• 10Y*: 1.79%

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

ACSNX vs. VBISX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
ACSNX American Century Short Duration Fund	0.86%	5.65%	4.69%	4.72%	-4.68%	0.97%	4.03%	3.95%	1.35%	1.42%
VBISX Vanguard Short-Term Bond Index Fund	0.26%	5.67%	3.66%	4.54%	-5.61%	-1.35%	4.63%	4.78%	1.27%	1.10%

Correlation

The correlation between ACSNX and VBISX is 0.83, 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	0.83
Correlation (3Y) Calculated over the trailing 3-year period	0.85
Correlation (5Y) Calculated over the trailing 5-year period	0.83
Correlation (10Y) Calculated over the trailing 10-year period	0.74
Correlation (All Time) Calculated using the full available price history since Dec 4, 2006	0.72

The correlation between ACSNX and VBISX shifts across timeframes, from 0.72 (all time) to 0.85 (3 years), reflecting how their relationship changes across market environments.

Return for Risk

ACSNX vs. VBISX — Risk / Return Rank

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

ACSNX

ACSNX Risk / Return Rank: 79
ACSNX Sharpe Ratio Rank: 60
ACSNX Sortino Ratio Rank: 92
ACSNX Omega Ratio Rank: 90
ACSNX Calmar Ratio Rank: 77
ACSNX Martin Ratio Rank: 77

VBISX

VBISX Risk / Return Rank: 37
VBISX Sharpe Ratio Rank: 33
VBISX Sortino Ratio Rank: 43
VBISX Omega Ratio Rank: 39
VBISX Calmar Ratio Rank: 40
VBISX Martin Ratio Rank: 33

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.

ACSNX vs. VBISX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for American Century Short Duration Fund (ACSNX) and Vanguard Short-Term Bond Index Fund (VBISX). 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.

	ACSNX	VBISX	Difference
Sharpe ratio: Return per unit of total volatility	2.29	1.64	+0.65
Sortino ratio: Return per unit of downside risk	4.60	2.75	+1.85
Omega ratio: Gain probability vs. loss probability	1.64	1.33	+0.31
Calmar ratio: Return relative to maximum drawdown	3.51	2.37	+1.14
Martin ratio: Return relative to average drawdown	14.48	7.61	+6.87
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

ACSNX vs. VBISX - Sharpe Ratio Comparison

The current ACSNX Sharpe Ratio is 2.29, which is higher than the VBISX Sharpe Ratio of 1.64. The chart below compares the historical Sharpe Ratios of ACSNX and VBISX, 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

	ACSNX	VBISX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	2.29	1.64	+0.65
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	1.00	0.49	+0.51
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	1.22	0.75	+0.46
Sharpe Ratio (All Time) Calculated using the full available price history	1.38	1.34	+0.04

Drawdowns

ACSNX vs. VBISX - Drawdown Comparison

The maximum ACSNX drawdown since its inception was -6.50%, smaller than the maximum VBISX drawdown of -8.79%. Use the drawdown chart below to compare losses from any high point for ACSNX and VBISX.

Drawdown Indicators

	ACSNX	VBISX	Difference
Max Drawdown Largest peak-to-trough decline	-6.50%	-8.79%	+2.29%
Max Drawdown (1Y) Largest decline over 1 year	-1.21%	-1.54%	+0.33%
Max Drawdown (3Y) Largest decline over 3 years	-1.21%	-1.55%	+0.34%
Max Drawdown (5Y) Largest decline over 5 years	-6.50%	-8.72%	+2.22%
Max Drawdown (10Y) Largest decline over 10 years	-6.50%	-8.79%	+2.29%
Current Drawdown Current decline from peak	-0.10%	-0.66%	+0.56%
Average Drawdown Average peak-to-trough decline	-0.59%	-0.87%	+0.28%
Ulcer Index Depth and duration of drawdowns from previous peaks	0.29%	0.48%	-0.19%

Volatility

ACSNX vs. VBISX - Volatility Comparison

The current volatility for American Century Short Duration Fund (ACSNX) is 0.61%, while Vanguard Short-Term Bond Index Fund (VBISX) has a volatility of 0.69%. This indicates that ACSNX experiences smaller price fluctuations and is considered to be less risky than VBISX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	ACSNX	VBISX	Difference
Volatility (1M) Calculated over the trailing 1-month period	0.61%	0.69%	-0.08%
Volatility (6M) Calculated over the trailing 6-month period	1.36%	1.59%	-0.23%
Volatility (1Y) Calculated over the trailing 1-year period	1.86%	2.24%	-0.38%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	2.20%	2.94%	-0.74%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	1.91%	2.38%	-0.47%

ACSNX vs. VBISX - Expense Ratio Comparison

ACSNX has a 0.57% expense ratio, which is higher than VBISX's 0.15% expense ratio.

Dividends

ACSNX vs. VBISX - Dividend Comparison

ACSNX's dividend yield for the trailing twelve months is around 4.38%, more than VBISX's 3.90% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
ACSNX American Century Short Duration Fund	4.38%	4.55%	4.56%	3.96%	1.60%	1.74%	1.51%	2.59%	2.53%	1.91%	1.62%	1.73%
VBISX Vanguard Short-Term Bond Index Fund	3.90%	3.44%	3.29%	2.10%	1.38%	1.16%	1.72%	2.16%	1.92%	1.58%	1.42%	1.34%

Frequently Asked Questions

Can I hold both ACSNX and VBISX in my portfolio?

ACSNX and VBISX have a correlation of 0.83, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, ACSNX or VBISX?

VBISX has higher volatility (0.69%) compared to ACSNX (0.61%). In terms of maximum drawdown, ACSNX dropped -6.50% vs VBISX's -8.79%.

Which has better risk-adjusted returns?

ACSNX currently has the higher Sharpe Ratio (2.29 vs 1.64), 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.