ISTB vs. FLDB

Last updated Jun 4, 2026

ISTB (iShares Core 1-5 Year USD Bond ETF) and FLDB (Fidelity Low Duration Bond ETF) are both Short-Term Bond funds. ISTB is passively managed, while FLDB is actively managed. Over the past year, ISTB returned 4.19% vs 4.19% for FLDB. At a 0.33 correlation, their price movements are largely independent. ISTB charges 0.06%/yr vs 0.20%/yr for FLDB.

Performance

ISTB vs. FLDB - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in iShares Core 1-5 Year USD Bond ETF (ISTB) and Fidelity Low Duration Bond ETF (FLDB). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, ISTB achieves a 0.49% return, which is significantly lower than FLDB's 1.28% return.

ISTB

• 1D: -0.08%
• 1M: 0.15%
• YTD: 0.49%
• 6M: 0.71%
• 1Y: 4.19%
• 3Y*: 4.95%
• 5Y*: 1.85%
• 10Y*: 2.27%

FLDB

• 1D: -0.13%
• 1M: 0.19%
• YTD: 1.28%
• 6M: 1.64%
• 1Y: 4.19%
• 3Y*: —
• 5Y*: —
• 10Y*: —

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

ISTB vs. FLDB - Yearly Performance Comparison

	2026 (YTD)	2025	2024
ISTB iShares Core 1-5 Year USD Bond ETF	0.49%	6.36%	4.73%
FLDB Fidelity Low Duration Bond ETF	1.28%	4.93%	4.29%

Correlation

The correlation between ISTB and FLDB is 0.34, which is low. Their price movements are largely independent, making them effective diversification partners.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.34
Correlation (All Time) Calculated using the full available price history since Feb 27, 2024	0.33

Return for Risk

ISTB vs. FLDB — Risk / Return Rank

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

ISTB

ISTB Risk / Return Rank: 73
ISTB Sharpe Ratio Rank: 71
ISTB Sortino Ratio Rank: 81
ISTB Omega Ratio Rank: 77
ISTB Calmar Ratio Rank: 67
ISTB Martin Ratio Rank: 68

FLDB

FLDB Risk / Return Rank: 98
FLDB Sharpe Ratio Rank: 97
FLDB Sortino Ratio Rank: 98
FLDB Omega Ratio Rank: 98
FLDB Calmar Ratio Rank: 99
FLDB Martin Ratio Rank: 99

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.

ISTB vs. FLDB - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for iShares Core 1-5 Year USD Bond ETF (ISTB) and Fidelity Low Duration Bond ETF (FLDB). 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.

	ISTB	FLDB	Difference
Sharpe ratio: Return per unit of total volatility	2.37	4.67	-2.30
Sortino ratio: Return per unit of downside risk	3.69	8.43	-4.73
Omega ratio: Gain probability vs. loss probability	1.46	2.11	-0.65
Calmar ratio: Return relative to maximum drawdown	3.34	25.08	-21.74
Martin ratio: Return relative to average drawdown	12.72	93.63	-80.92
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

ISTB vs. FLDB - Sharpe Ratio Comparison

The current ISTB Sharpe Ratio is 2.37, which is lower than the FLDB Sharpe Ratio of 4.67. The chart below compares the historical Sharpe Ratios of ISTB and FLDB, 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

	ISTB	FLDB	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	2.37	4.67	-2.30
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.67	—	—
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.91	—	—
Sharpe Ratio (All Time) Calculated using the full available price history	0.84	3.56	-2.72

Drawdowns

ISTB vs. FLDB - Drawdown Comparison

The maximum ISTB drawdown since its inception was -9.34%, which is greater than FLDB's maximum drawdown of -0.49%. Use the drawdown chart below to compare losses from any high point for ISTB and FLDB.

Drawdown Indicators

	ISTB	FLDB	Difference
Max Drawdown Largest peak-to-trough decline	-9.34%	-0.49%	-8.85%
Max Drawdown (1Y) Largest decline over 1 year	-1.26%	-0.17%	-1.09%
Max Drawdown (3Y) Largest decline over 3 years	-1.36%	—	—
Max Drawdown (5Y) Largest decline over 5 years	-9.34%	—	—
Max Drawdown (10Y) Largest decline over 10 years	-9.34%	—	—
Current Drawdown Current decline from peak	-0.42%	-0.13%	-0.29%
Average Drawdown Average peak-to-trough decline	-1.22%	-0.05%	-1.17%
Ulcer Index Depth and duration of drawdowns from previous peaks	0.33%	0.04%	+0.29%

Volatility

ISTB vs. FLDB - Volatility Comparison

iShares Core 1-5 Year USD Bond ETF (ISTB) has a higher volatility of 0.54% compared to Fidelity Low Duration Bond ETF (FLDB) at 0.34%. This indicates that ISTB's price experiences larger fluctuations and is considered to be riskier than FLDB based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	ISTB	FLDB	Difference
Volatility (1M) Calculated over the trailing 1-month period	0.54%	0.34%	+0.20%
Volatility (6M) Calculated over the trailing 6-month period	1.28%	0.61%	+0.67%
Volatility (1Y) Calculated over the trailing 1-year period	1.77%	0.91%	+0.86%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	2.79%	1.31%	+1.48%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	2.51%	1.31%	+1.20%

ISTB vs. FLDB - Expense Ratio Comparison

ISTB has a 0.06% expense ratio, which is lower than FLDB's 0.20% expense ratio. Despite the difference, both funds are considered low-cost compared to the broader market, where average expense ratios usually range from 0.3% to 0.9%.

Dividends

ISTB vs. FLDB - Dividend Comparison

ISTB's dividend yield for the trailing twelve months is around 4.25%, less than FLDB's 4.45% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
FLDB Fidelity Low Duration Bond ETF	4.45%	4.72%	3.58%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%
ISTB iShares Core 1-5 Year USD Bond ETF	4.25%	4.12%	3.83%	2.97%	2.01%	1.69%	2.20%	2.75%	2.57%	2.06%	1.90%	1.58%

Frequently Asked Questions

Can I hold both ISTB and FLDB in my portfolio?

ISTB and FLDB have a correlation of 0.34, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, ISTB or FLDB?

ISTB has higher volatility (0.54%) compared to FLDB (0.34%). In terms of maximum drawdown, ISTB dropped -9.34% vs FLDB's -0.49%.

Which ETF is better, ISTB or FLDB?

On 1-year performance, FLDB leads with 4.19% vs 4.19% for ISTB. On fees, ISTB is cheaper at 0.06% per year. On volatility, FLDB has been the lower-risk option at 0.34%. The better choice depends on whether you care most about return, fees, risk, or income.

Which ETF has performed better, ISTB or FLDB?

Over the 1-year period, FLDB has performed better with a 4.19% return vs 4.19%. Past performance does not guarantee future results, so compare this with risk, fees, and fund exposure.

Which ETF is cheaper, ISTB or FLDB?

ISTB is cheaper with a 0.06% expense ratio, compared with 0.20% for FLDB.

Which ETF pays a higher dividend yield, ISTB or FLDB?

FLDB has the higher dividend yield at 4.45%, compared with 4.25% for ISTB.

What is the main difference between ISTB and FLDB?

They also come from different issuers: iShares and Fidelity. Their fees differ too: 0.06% for ISTB and 0.20% for FLDB.

Which has better risk-adjusted returns?

FLDB currently has the higher Sharpe Ratio (4.67 vs 2.37), 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.