MBDFX vs. WFBIX

Last updated Jun 4, 2026

MBDFX (AMG GW&K Core Bond ESG Fund) and WFBIX (iShares U.S. Aggregate Bond Index Fund) are both Intermediate Core Bond funds. Over the past 10 years, MBDFX returned 1.27%/yr vs 1.96%/yr for WFBIX. Their correlation of 0.88 suggests significant overlap in exposure. MBDFX charges 0.56%/yr vs 0.05%/yr for WFBIX.

Performance

MBDFX vs. WFBIX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in AMG GW&K Core Bond ESG Fund (MBDFX) and iShares U.S. Aggregate Bond Index Fund (WFBIX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, MBDFX achieves a -0.05% return, which is significantly lower than WFBIX's 0.43% return. Over the past 10 years, MBDFX has underperformed WFBIX with an annualized return of 1.27%, while WFBIX has yielded a comparatively higher 1.96% annualized return.

MBDFX

• 1D: 0.00%
• 1M: 0.56%
• YTD: -0.05%
• 6M: -0.28%
• 1Y: 5.01%
• 3Y*: 3.84%
• 5Y*: -0.46%
• 10Y*: 1.27%

WFBIX

• 1D: 0.00%
• 1M: 0.45%
• YTD: 0.43%
• 6M: 0.32%
• 1Y: 5.35%
• 3Y*: 5.33%
• 5Y*: 0.99%
• 10Y*: 1.96%

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

MBDFX vs. WFBIX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
MBDFX AMG GW&K Core Bond ESG Fund	-0.05%	7.29%	1.24%	5.73%	-13.85%	-3.34%	7.33%	9.70%	-1.11%	3.88%
WFBIX iShares U.S. Aggregate Bond Index Fund	0.43%	7.16%	1.43%	9.65%	-13.03%	-1.79%	7.40%	8.72%	-0.08%	3.39%

Correlation

The correlation between MBDFX and WFBIX is 0.92, 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	0.92
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	0.94
Correlation (All Time) Calculated using the full available price history since Jul 6, 1993	0.88

The correlation between MBDFX and WFBIX has been stable across timeframes, ranging from 0.88 to 0.95 - a consistent structural relationship.

Return for Risk

MBDFX vs. WFBIX — Risk / Return Rank

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

MBDFX

MBDFX Risk / Return Rank: 19
MBDFX Sharpe Ratio Rank: 21
MBDFX Sortino Ratio Rank: 21
MBDFX Omega Ratio Rank: 20
MBDFX Calmar Ratio Rank: 18
MBDFX Martin Ratio Rank: 16

WFBIX

WFBIX Risk / Return Rank: 22
WFBIX Sharpe Ratio Rank: 22
WFBIX Sortino Ratio Rank: 24
WFBIX Omega Ratio Rank: 22
WFBIX Calmar Ratio Rank: 23
WFBIX Martin Ratio Rank: 20

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.

MBDFX vs. WFBIX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for AMG GW&K Core Bond ESG Fund (MBDFX) and iShares U.S. Aggregate Bond Index Fund (WFBIX). 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.

	MBDFX	WFBIX	Difference
Sharpe ratio: Return per unit of total volatility	1.31	1.36	-0.05
Sortino ratio: Return per unit of downside risk	1.92	2.04	-0.12
Omega ratio: Gain probability vs. loss probability	1.23	1.25	-0.01
Calmar ratio: Return relative to maximum drawdown	1.56	1.78	-0.23
Martin ratio: Return relative to average drawdown	4.52	5.34	-0.82
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

MBDFX vs. WFBIX - Sharpe Ratio Comparison

The current MBDFX Sharpe Ratio is 1.31, which is comparable to the WFBIX Sharpe Ratio of 1.36. The chart below compares the historical Sharpe Ratios of MBDFX and WFBIX, 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

	MBDFX	WFBIX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	1.31	1.36	-0.05
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	-0.07	0.16	-0.23
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.25	0.38	-0.13
Sharpe Ratio (All Time) Calculated using the full available price history	0.48	0.94	-0.47

Drawdowns

MBDFX vs. WFBIX - Drawdown Comparison

The maximum MBDFX drawdown since its inception was -20.66%, which is greater than WFBIX's maximum drawdown of -18.68%. Use the drawdown chart below to compare losses from any high point for MBDFX and WFBIX.

Drawdown Indicators

	MBDFX	WFBIX	Difference
Max Drawdown Largest peak-to-trough decline	-20.66%	-18.68%	-1.98%
Max Drawdown (1Y) Largest decline over 1 year	-3.25%	-3.02%	-0.23%
Max Drawdown (3Y) Largest decline over 3 years	-6.99%	-6.09%	-0.90%
Max Drawdown (5Y) Largest decline over 5 years	-20.54%	-17.84%	-2.70%
Max Drawdown (10Y) Largest decline over 10 years	-20.66%	-18.68%	-1.98%
Current Drawdown Current decline from peak	-4.51%	-1.50%	-3.01%
Average Drawdown Average peak-to-trough decline	-3.96%	-2.26%	-1.70%
Ulcer Index Depth and duration of drawdowns from previous peaks	1.11%	1.00%	+0.11%

Volatility

MBDFX vs. WFBIX - Volatility Comparison

AMG GW&K Core Bond ESG Fund (MBDFX) and iShares U.S. Aggregate Bond Index Fund (WFBIX) have volatilities of 1.35% and 1.34%, respectively, indicating that both stocks experience similar levels of price fluctuations. This suggests that the risk associated with both stocks, as measured by volatility, is nearly the same. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	MBDFX	WFBIX	Difference
Volatility (1M) Calculated over the trailing 1-month period	1.35%	1.34%	+0.01%
Volatility (6M) Calculated over the trailing 6-month period	2.79%	2.83%	-0.04%
Volatility (1Y) Calculated over the trailing 1-year period	3.87%	3.97%	-0.10%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	6.15%	6.40%	-0.25%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	5.06%	5.17%	-0.11%

MBDFX vs. WFBIX - Expense Ratio Comparison

MBDFX has a 0.56% expense ratio, which is higher than WFBIX's 0.05% expense ratio.

Dividends

MBDFX vs. WFBIX - Dividend Comparison

MBDFX's dividend yield for the trailing twelve months is around 3.47%, less than WFBIX's 3.91% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
MBDFX AMG GW&K Core Bond ESG Fund	3.47%	3.66%	3.50%	2.92%	2.16%	2.35%	1.84%	2.40%	2.30%	2.10%	2.06%	4.17%
WFBIX iShares U.S. Aggregate Bond Index Fund	3.91%	3.78%	3.68%	6.82%	2.60%	2.04%	2.43%	2.88%	2.71%	2.24%	2.25%	2.20%

Frequently Asked Questions

Can I hold both MBDFX and WFBIX in my portfolio?

With a correlation of 0.92, MBDFX and WFBIX 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, MBDFX or WFBIX?

MBDFX has higher volatility (1.35%) compared to WFBIX (1.34%). In terms of maximum drawdown, MBDFX dropped -20.66% vs WFBIX's -18.68%.

Which has better risk-adjusted returns?

WFBIX currently has the higher Sharpe Ratio (1.36 vs 1.31), 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.