MIDLX vs. BBTBX

Last updated Jun 9, 2026

MIDLX (MFS International New Discovery Fund Class R6) and BBTBX (Bridge Builder Core Bond Fund) are both mutual funds - MIDLX is a Foreign Small & Mid Cap Equities fund tracking the MSCI All Country World ex-US Small Mid Cap Index, while BBTBX is a Intermediate Core Bond fund managed by Bridge Builder. Over the past 10 years, MIDLX returned 6.41%/yr vs 1.77%/yr for BBTBX. At a 0.06 correlation, their price movements are largely independent. MIDLX charges 0.91%/yr vs 0.13%/yr for BBTBX.

Performance

MIDLX vs. BBTBX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in MFS International New Discovery Fund Class R6 (MIDLX) and Bridge Builder Core Bond Fund (BBTBX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, MIDLX achieves a 3.83% return, which is significantly higher than BBTBX's -0.41% return. Over the past 10 years, MIDLX has outperformed BBTBX with an annualized return of 6.41%, while BBTBX has yielded a comparatively lower 1.77% annualized return.

MIDLX

• 1D: -2.35%
• 1M: -3.37%
• YTD: 3.83%
• 6M: 4.94%
• 1Y: 7.50%
• 3Y*: 9.96%
• 5Y*: 2.83%
• 10Y*: 6.41%

BBTBX

• 1D: -0.45%
• 1M: -0.51%
• YTD: -0.41%
• 6M: 0.07%
• 1Y: 5.06%
• 3Y*: 4.05%
• 5Y*: 0.08%
• 10Y*: 1.77%

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

MIDLX vs. BBTBX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
MIDLX MFS International New Discovery Fund Class R6	3.83%	17.03%	3.33%	13.21%	-18.52%	5.17%	10.15%	24.97%	-10.29%	30.65%
BBTBX Bridge Builder Core Bond Fund	-0.41%	7.82%	1.89%	5.41%	-13.49%	-1.12%	8.54%	9.15%	0.13%	4.14%

Correlation

The correlation between MIDLX and BBTBX is 0.41, which is low. Their price movements are largely independent, making them effective diversification partners.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.41
Correlation (3Y) Calculated over the trailing 3-year period	0.33
Correlation (5Y) Calculated over the trailing 5-year period	0.26
Correlation (10Y) Calculated over the trailing 10-year period	0.12
Correlation (All Time) Calculated using the full available price history since Oct 31, 2013	0.06

Over the past year, MIDLX and BBTBX have become more correlated (0.41) than their long-term average of 0.06, meaning their price movements have been converging.

Return for Risk

MIDLX vs. BBTBX — Risk / Return Rank

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

MIDLX

MIDLX Risk / Return Rank: 9
MIDLX Sharpe Ratio Rank: 9
MIDLX Sortino Ratio Rank: 9
MIDLX Omega Ratio Rank: 9
MIDLX Calmar Ratio Rank: 8
MIDLX Martin Ratio Rank: 9

BBTBX

BBTBX Risk / Return Rank: 18
BBTBX Sharpe Ratio Rank: 18
BBTBX Sortino Ratio Rank: 18
BBTBX Omega Ratio Rank: 17
BBTBX Calmar Ratio Rank: 21
BBTBX Martin Ratio Rank: 18

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.

MIDLX vs. BBTBX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for MFS International New Discovery Fund Class R6 (MIDLX) and Bridge Builder Core Bond Fund (BBTBX). 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.

	MIDLX	BBTBX	Difference
Sharpe ratio: Return per unit of total volatility	0.64	1.10	-0.45
Sortino ratio: Return per unit of downside risk	0.98	1.60	-0.62
Omega ratio: Gain probability vs. loss probability	1.12	1.19	-0.07
Calmar ratio: Return relative to maximum drawdown	0.64	1.52	-0.87
Martin ratio: Return relative to average drawdown	2.20	4.34	-2.14
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

MIDLX vs. BBTBX - Sharpe Ratio Comparison

The current MIDLX Sharpe Ratio is 0.64, which is lower than the BBTBX Sharpe Ratio of 1.10. The chart below compares the historical Sharpe Ratios of MIDLX and BBTBX, 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

	MIDLX	BBTBX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	0.64	1.10	-0.45
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.21	0.01	+0.20
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.46	0.36	+0.10
Sharpe Ratio (All Time) Calculated using the full available price history	0.57	0.37	+0.20

Drawdowns

MIDLX vs. BBTBX - Drawdown Comparison

The maximum MIDLX drawdown since its inception was -34.70%, which is greater than BBTBX's maximum drawdown of -18.54%. Use the drawdown chart below to compare losses from any high point for MIDLX and BBTBX.

Drawdown Indicators

	MIDLX	BBTBX	Difference
Max Drawdown Largest peak-to-trough decline	-34.70%	-18.54%	-16.16%
Max Drawdown (1Y) Largest decline over 1 year	-11.75%	-2.97%	-8.78%
Max Drawdown (3Y) Largest decline over 3 years	-13.15%	-6.32%	-6.83%
Max Drawdown (5Y) Largest decline over 5 years	-33.58%	-18.54%	-15.04%
Max Drawdown (10Y) Largest decline over 10 years	-34.70%	-18.54%	-16.16%
Current Drawdown Current decline from peak	-4.51%	-1.94%	-2.57%
Average Drawdown Average peak-to-trough decline	-6.92%	-3.91%	-3.01%
Ulcer Index Depth and duration of drawdowns from previous peaks	3.42%	1.02%	+2.40%

Volatility

MIDLX vs. BBTBX - Volatility Comparison

MFS International New Discovery Fund Class R6 (MIDLX) has a higher volatility of 3.57% compared to Bridge Builder Core Bond Fund (BBTBX) at 1.34%. This indicates that MIDLX's price experiences larger fluctuations and is considered to be riskier than BBTBX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	MIDLX	BBTBX	Difference
Volatility (1M) Calculated over the trailing 1-month period	3.57%	1.34%	+2.23%
Volatility (6M) Calculated over the trailing 6-month period	9.79%	2.96%	+6.83%
Volatility (1Y) Calculated over the trailing 1-year period	11.73%	4.10%	+7.63%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	13.24%	5.97%	+7.27%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	14.02%	4.94%	+9.08%

MIDLX vs. BBTBX - Expense Ratio Comparison

MIDLX has a 0.91% expense ratio, which is higher than BBTBX's 0.13% expense ratio.

Dividends

MIDLX vs. BBTBX - Dividend Comparison

MIDLX's dividend yield for the trailing twelve months is around 3.25%, less than BBTBX's 4.09% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
BBTBX Bridge Builder Core Bond Fund	4.09%	4.58%	3.92%	2.86%	2.26%	2.38%	4.73%	3.39%	3.02%	2.67%	0.95%	0.17%
MIDLX MFS International New Discovery Fund Class R6	3.25%	3.37%	10.08%	4.21%	5.85%	5.19%	4.03%	4.36%	6.82%	1.63%	1.09%	1.25%

Frequently Asked Questions

Can I hold both MIDLX and BBTBX in my portfolio?

MIDLX and BBTBX have a correlation of 0.41, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, MIDLX or BBTBX?

MIDLX has higher volatility (3.57%) compared to BBTBX (1.34%). In terms of maximum drawdown, MIDLX dropped -34.70% vs BBTBX's -18.54%.

Which has better risk-adjusted returns?

BBTBX currently has the higher Sharpe Ratio (1.10 vs 0.64), 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.