BIRDX vs. WFSPX
BIRDX (iShares Developed Real Estate Index Fund) and WFSPX (iShares S&P 500 Index Fund Class K) are both mutual funds - BIRDX is a REIT fund managed by BlackRock, while WFSPX is a S&P 500 fund tracking the S&P 500 Index. Over the past 10 years, BIRDX returned 4.01%/yr vs 15.50%/yr for WFSPX. A 0.62 correlation means they provide meaningful diversification when combined. BIRDX charges 0.19%/yr vs 0.03%/yr for WFSPX.
Performance
BIRDX vs. WFSPX - Performance Comparison
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Returns By Period
In the year-to-date period, BIRDX achieves a 9.99% return, which is significantly higher than WFSPX's 8.09% return. Over the past 10 years, BIRDX has underperformed WFSPX with an annualized return of 4.01%, while WFSPX has yielded a comparatively higher 15.50% annualized return.
BIRDX
- 1D
- 0.45%
- 1M
- -0.22%
- YTD
- 9.99%
- 6M
- 9.59%
- 1Y
- 14.69%
- 3Y*
- 11.70%
- 5Y*
- 1.94%
- 10Y*
- 4.01%
WFSPX
- 1D
- -0.10%
- 1M
- -2.04%
- YTD
- 8.09%
- 6M
- 6.76%
- 1Y
- 22.17%
- 3Y*
- 20.73%
- 5Y*
- 13.01%
- 10Y*
- 15.50%
BIRDX vs. WFSPX - Yearly Performance Comparison
| 2026 (YTD) | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | |
|---|---|---|---|---|---|---|---|---|---|---|
BIRDX iShares Developed Real Estate Index Fund | 9.99% | 10.27% | 1.49% | 10.38% | -24.68% | 26.90% | -8.24% | 22.33% | -4.80% | 7.56% |
WFSPX iShares S&P 500 Index Fund Class K | 8.09% | 17.83% | 24.94% | 26.25% | -18.14% | 28.63% | 18.43% | 31.45% | -4.83% | 21.27% |
Correlation
The correlation between BIRDX and WFSPX is 0.37, which is low. Their price movements are largely independent, making them effective diversification partners.
| Correlation | |
|---|---|
Correlation (1Y) Calculated over the trailing 1-year period | 0.37 |
Correlation (3Y) Calculated over the trailing 3-year period | 0.51 |
Correlation (5Y) Calculated over the trailing 5-year period | 0.62 |
Correlation (10Y) Calculated over the trailing 10-year period | 0.61 |
Correlation (All Time) Calculated using the full available price history since Jan 4, 2016 | 0.62 |
Over the past year, the correlation between BIRDX and WFSPX has dropped to 0.37 - well below their long-term average of 0.62, suggesting their price drivers have been diverging.
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Return for Risk
BIRDX vs. WFSPX — Risk / Return Rank
BIRDX
WFSPX
BIRDX vs. WFSPX - Risk-Adjusted Trends Comparison
This table presents a comparison of risk-adjusted performance metrics for iShares Developed Real Estate Index Fund (BIRDX) and iShares S&P 500 Index Fund Class K (WFSPX). 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.
Values are calculated on a 1-year rolling basis and updated daily. Risk-adjusted metrics are more stable over longer periods — use the period switch above to explore them.
| BIRDX | WFSPX | Difference | |
|---|---|---|---|
| Sharpe ratioReturn per unit of total volatility | -0.74 | ||
| Sortino ratioReturn per unit of downside risk | -0.96 | ||
| Omega ratioGain probability vs. loss probability | 1.19 | 1.32 | -0.13 |
| Calmar ratioReturn relative to maximum drawdown | 1.27 | 2.50 | -1.24 |
| Martin ratioReturn relative to average drawdown | 4.66 | 11.18 | -6.52 |
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Drawdowns
BIRDX vs. WFSPX - Drawdown Comparison
The maximum BIRDX drawdown since its inception was -43.03%, smaller than the maximum WFSPX drawdown of -58.21%. Use the drawdown chart below to compare losses from any high point for BIRDX and WFSPX.
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Drawdown Indicators
| BIRDX | WFSPX | Difference | |
|---|---|---|---|
Max DrawdownLargest peak-to-trough decline | -43.03% | -58.21% | +15.18% |
Max Drawdown (1Y)Largest decline over 1 year | -10.04% | -8.90% | -1.14% |
Max Drawdown (3Y)Largest decline over 3 years | -27.40% | -18.74% | -8.66% |
Max Drawdown (5Y)Largest decline over 5 years | -32.54% | -24.51% | -8.03% |
Max Drawdown (10Y)Largest decline over 10 years | -43.03% | -33.74% | -9.29% |
Current DrawdownCurrent decline from peak | -3.94% | -3.22% | -0.72% |
Average DrawdownAverage peak-to-trough decline | -10.81% | -12.75% | +1.94% |
Ulcer IndexDepth and duration of drawdowns from previous peaks | 2.73% | 1.99% | +0.74% |
Volatility
BIRDX vs. WFSPX - Volatility Comparison
The current volatility for iShares Developed Real Estate Index Fund (BIRDX) is 4.19%, while iShares S&P 500 Index Fund Class K (WFSPX) has a volatility of 4.88%. This indicates that BIRDX experiences smaller price fluctuations and is considered to be less risky than WFSPX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.
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Volatility by Period
| BIRDX | WFSPX | Difference | |
|---|---|---|---|
Volatility (1M)Calculated over the trailing 1-month period | 4.19% | 4.88% | -0.69% |
Volatility (6M)Calculated over the trailing 6-month period | 9.41% | 9.89% | -0.48% |
Volatility (1Y)Calculated over the trailing 1-year period | 12.21% | 12.53% | -0.32% |
Volatility (5Y)Calculated over the trailing 5-year period, annualized | 19.29% | 16.98% | +2.31% |
Volatility (10Y)Calculated over the trailing 10-year period, annualized | 19.09% | 18.04% | +1.05% |
BIRDX vs. WFSPX - Expense Ratio Comparison
BIRDX has a 0.19% expense ratio, which is higher than WFSPX's 0.03% expense ratio. However, both funds are considered low-cost compared to the broader market, where average expense ratios usually range from 0.3% to 0.9%.
Dividends
BIRDX vs. WFSPX - Dividend Comparison
BIRDX's dividend yield for the trailing twelve months is around 6.46%, more than WFSPX's 1.62% yield.
| Position | TTM | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
BIRDX iShares Developed Real Estate Index Fund | 6.46% | 6.84% | 23.69% | 2.99% | 1.24% | 4.18% | 1.91% | 6.67% | 4.18% | 1.70% | 2.24% | 0.00% |
WFSPX iShares S&P 500 Index Fund Class K | 1.62% | 1.72% | 1.41% | 1.50% | 2.02% | 1.82% | 1.66% | 1.99% | 2.00% | 1.62% | 2.37% | 2.49% |
Frequently Asked Questions
BIRDX and WFSPX have a correlation of 0.37, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.
WFSPX has higher volatility (4.88%) compared to BIRDX (4.19%). In terms of maximum drawdown, BIRDX dropped -43.03% vs WFSPX's -58.21%.
WFSPX currently has the higher Sharpe Ratio (1.78 vs 1.04), 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.
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