Z vs OPEN: Stock Returns, Risk & Volatility (2026)

Q: Which is a better investment: Z or OPEN?

Over the past year, OPEN looks like the better investment: it had higher total return (OPEN +259.9% vs Z -40.6%) and a higher Sharpe ratio (OPEN 1.48 vs Z -1.09). On risk, Z was less volatile (Z 43.3% vs OPEN 166.7%), Z had a smaller max drawdown (Z -52.6% vs OPEN -64.2%), and Z had less severe losses on the worst 5% of days (Expected Shortfall of Z -6.67% vs OPEN -17.12%).

Written by Gale Finance Team

Reviewed by Sid Kalla CFA Charterholder

Quick answer

Which is a better investment: Z or OPEN?

Over the past year, OPEN outperformed (-40.6% vs +259.9%) with a Sharpe ratio of 1.48.

Total Return

Z -40.6%

OPEN WIN +259.9%

Sharpe Ratio

Z -1.09

OPEN WIN 1.48

Annualized Volatility

Z WIN 43.3%

OPEN 166.7%

Max Drawdown

Z WIN -52.6%

OPEN -64.2%

Analysis period: 2025-02-27 to 2026-02-25

Z Total Return

↓ -40.6%

OPEN Total Return

↑ +259.9%

Relative Performance of Z vs OPEN (Normalized to 100)

Z OPEN

Normalized to 100 at start date for comparison

Key Takeaways

Total Return: Z delivered a -40.6% total return, while OPEN returned +259.9% over the same period. OPEN outperformed on total returns.
Risk-Adjusted Return (Sharpe Ratio): Z had a negative Sharpe (-1.09) while OPEN was positive (1.48), indicating OPEN had meaningfully better risk-adjusted performance in this period.
Volatility (Annualized): OPEN was more volatile, with 166.7% annualized volatility, versus 43.3% for Z.
Maximum Drawdown: Z's maximum drawdown was -52.6%, while OPEN experienced a deeper drawdown of -64.2%.
Tail Risk (VaR & Expected Shortfall): At the 5% level (daily log returns), Z's VaR was -4.58% and its Expected Shortfall (CVaR) was -6.67%; OPEN's were -11.78% and -17.12%. VaR is the cutoff; Expected Shortfall is the average move on the worst days.
Skew & Kurtosis: Skew: Z -1.09 vs OPEN 1.44. Excess kurtosis: Z 6.58 vs OPEN 6.82. Negative skew leans downside; higher excess kurtosis means fatter tails.
Tail Days & Extremes: 2σ tail days (down/up): Z 6/5, OPEN 3/7. Worst day: Z -16.54% (2026-02-11) vs OPEN -24.60% (2025-08-06). Best day: Z +8.49% (2025-04-09) vs OPEN +79.52% (2025-09-11).
Risk ratios: Sortino - Z: -1.40 vs. OPEN: 3.03 , Calmar - Z: -0.78 vs. OPEN: 4.09 , Sterling - Z: -1.21 vs. OPEN: 7.36 , Treynor - Z: -0.42 vs. OPEN: 1.43 , Ulcer Index - Z: 18.73% vs. OPEN: 36.83%

Zillow vs Opendoor Correlation

0.22 Average Correlation

Zillow and Opendoor are weakly correlated over the past year. With a correlation of 0.22, these assets show meaningful independence, offering diversification benefits when held together.

For portfolio construction, this weak correlation suggests that combining Z and OPEN could reduce overall portfolio variance. However, correlations can increase during market stress.

Metric	Value
Current (30-day)	0.13
Average (full period)	0.22
Minimum	-0.08
Maximum	0.68

Correlation measures how closely two assets move together. Values near +1 indicate strong co-movement, near 0 indicates independence, and negative values indicate inverse movement.

Investment Comparison

If you invested $10,000 in each asset on February 27, 2025:

Z $5,936.84 -40.6%

OPEN $35,986.01 +259.9%

Difference: $30,049.17 (OPEN ahead)

Zillow and Opendoor: Risk Analysis

Zillow experienced its maximum drawdown of -52.6% from 2025-09-17 to 2026-02-23. It has not yet recovered to its previous peak.

Opendoor experienced its maximum drawdown of -64.2% from 2025-02-27 to 2025-06-25. It took 21 days to recover.

Smaller drawdowns and faster recoveries indicate lower downside risk and greater resilience during market stress.

Sharpe Ratio of Z and OPEN

Z Sharpe Ratio

↓ -1.09

OPEN Sharpe Ratio

↑ 1.48

Sharpe ratio measures return per unit of risk (volatility). A higher Sharpe indicates better risk-adjusted performance. Z had a negative Sharpe (-1.09) while OPEN was positive (1.48), indicating OPEN had meaningfully better risk-adjusted performance in this period.

A Sharpe above 1.0 is generally considered good, above 2.0 is excellent. Negative Sharpe means the asset underperformed the risk-free rate. Calculated on each asset's full 365-day lookback of available prices and annualized using the asset calendar (365 for crypto, 252 trading days for equities/ETFs/metals).

Sortino Ratio of Z and OPEN

Z Sortino Ratio

↓ -1.40

OPEN Sortino Ratio

↑ 3.03

Sortino ratio measures return per unit of downside risk. Unlike Sharpe, it only counts downside deviation (returns below the target return). OPEN had better downside-adjusted returns.

A higher Sortino is better. It's useful when upside volatility is common (crypto is the obvious example). Downside deviation: Z 33.9% vs OPEN 81.4%. Calculated on each asset's full 365-day lookback of available prices, using the daily risk-free rate as the target return, and annualized using the asset calendar (365 for crypto, 252 trading days for equities/ETFs/metals).

Calmar Ratio of Z and OPEN

Z Calmar Ratio

↓ -0.78

OPEN Calmar Ratio

↑ 4.09

Calmar ratio compares CAGR to maximum drawdown. Higher Calmar means more return per unit of worst drawdown. OPEN posted the higher Calmar ratio.

Calmar is computed on each asset's full 365-day lookback and uses the max drawdown over that same window.

Sterling Ratio of Z and OPEN

Z Sterling Ratio

↓ -1.21

OPEN Sterling Ratio

↑ 7.36

Sterling ratio measures excess return per unit of average drawdown (typically drawdowns worse than 10%). OPEN posted the higher Sterling ratio.

Sterling uses average drawdown events deeper than 10% and subtracts the risk-free rate to report excess return.

Treynor Ratio of Z and OPEN

Z Treynor Ratio

↓ -0.42

OPEN Treynor Ratio

↑ 1.43

Treynor ratio measures excess return per unit of market risk (beta) instead of total volatility. OPEN posted the higher Treynor ratio.

Treynor uses beta vs the S&P 500 (SPY) on shared dates and the average 3-month Treasury rate as the risk-free rate.

Ulcer Index of Z and OPEN

Z Ulcer Index

18.73%

OPEN Ulcer Index

36.83%

Ulcer Index captures drawdown depth and duration. Lower Ulcer Index means less drawdown pain. Z had the lower Ulcer Index (less drawdown pain).

Ulcer Index is computed from each asset's drawdown series over the full lookback window.

Tail Risk & Distribution Shape (1-Year): Zillow vs. Opendoor

This section looks at the shape of daily returns, not just the average. Tail stats are computed per asset on its own daily series (crypto includes weekends). We use daily log returns $\ln\left(\frac{P_t}{P_{t-1}}\right)$ so multi-day moves add cleanly.

Definitions: Value at Risk (VaR), Expected Shortfall, skew, kurtosis, and fat tails.

Metric (1-Year)	Z	OPEN
5% VaR (daily log return)	-4.58%	-11.78%
5% Expected Shortfall (CVaR)	-6.67% (worst 13 days)	-17.12% (worst 13 days)
Skew	-1.09	1.44
Excess kurtosis	6.58	6.82
2σ tail days (down / up)	6 / 5	3 / 7
Worst day	-16.54% (2026-02-11)	-24.60% (2025-08-06)
Best day	+8.49% (2025-04-09)	+79.52% (2025-09-11)

Downside co-moves (2σ) — 1-Year

Computed on shared dates only (n=249). A “2σ downside move” means a shared-close log return more than 2 standard deviations below that asset’s own mean on this shared-date series. Dates below show simple returns (%) for readability.

When OPEN has a big down day, Z also does

0.0%

0 / 3 days

When Z has a big down day, OPEN also does

0.0%

0 / 6 days

Show downside tail dates

Dates below are shared-date observations. The “Date” is the period end (close). Tail thresholds are computed on log returns, but the table shows simple returns (%) for readability. Returns are computed from the previous shared close to this one (for example, Friday → Monday includes weekend moves).

Days when both Z and OPEN had a big down day (2σ)

None in this window.

Days when Z had a big down day

Date (interval)	Z	OPEN
2025-04-10	-6.43%	-9.56%
2025-09-19 → 2025-09-22	-6.57%	-12.43%
2025-12-12 → 2025-12-15	-8.47%	-1.37%
2026-02-03	-5.73%	+6.43%
2026-02-11	-16.54%	+1.49%
2026-02-20 → 2026-02-23	-5.79%	-4.40%

Days when OPEN had a big down day

Date (interval)	Z	OPEN
2025-05-09	+0.04%	-23.07%
2025-07-23	+0.47%	-20.49%
2025-08-06	+3.25%	-24.60%

Read this as “how ugly the ugly days get”, not as a precise forecast. One-year samples are small, so tail estimates are inherently noisy.

Zillow vs Opendoor Volatility (Z vs OPEN)

Z Volatility

43.3%

±2.73% daily

OPEN Volatility

166.7%

±10.5% daily

Typical daily swing

±2.73%

OPEN

±10.5%

Zillow's annualized volatility of 43.3% means it typically moves ±2.73% on any given day.

Opendoor's annualized volatility of 166.7% means it typically moves ±10.5% on any given day.

OPEN's higher volatility means a wider path to returns — this can be attractive for tactical, shorter-term exposure, while Z's smoother profile may better suit long-term allocators seeking steadier growth.

For comparison, the S&P 500 typically has 15-18% annualized volatility, translating to roughly ±1% daily moves. Higher volatility means larger potential gains but also larger potential losses.

Zillow vs Opendoor Performance Over Time

Metric	Z	OPEN
30 Days	-34.9%	-15.2%
90 Days	-39.1%	-36%
180 Days	-46.3%	15.6%
1 Year	-40.6%	259.9%

Shorter time frames can show different leaders as market conditions change. Consider your investment horizon when comparing performance.

Full Comparison of Zillow vs. Opendoor (1-Year)

Metric	Z	OPEN
Total Return	-40.6%	+259.9%
Annualized Volatility	43.3%	166.7%
Sharpe Ratio	-1.09	1.48
Sortino Ratio	-1.40	3.03
Calmar Ratio	-0.78	4.09
Sterling Ratio	-1.21	7.36
Treynor Ratio	-0.42	1.43
Ulcer Index	18.73%	36.83%
Max Drawdown	-52.6%	-64.2%
Avg Correlation to S&P 500	0.41	0.24
5% VaR (daily log return)	-4.58%	-11.78%
5% Expected Shortfall (CVaR)	-6.67%	-17.12%
Skew	-1.09	1.44
Excess kurtosis	6.58	6.82
2σ tail days (down / up)	6 / 5	3 / 7

Audit this calculation

Formulas, inputs, and conventions used to compute the metrics on this page.

Inputs & conventions

Shared window for pair metrics: 2025-02-27 → 2026-02-25 (last shared close).
Rolling correlation sample (shared closes): 220 rolling 30-day values (from 249 shared daily returns).
Annualization (days/year): Z: 252 days/year; OPEN: 252 days/year.
Risk-free rate: Uses the 3-month U.S. Treasury yield (FRED: DGS3MO), averaged over each asset’s window:

Z: 4.20% over 2025-02-27 → 2026-02-25.

OPEN: 4.20% over 2025-02-27 → 2026-02-25.
Volatility drag (rule of thumb): Estimated from annualized volatility (simple returns). For the log-return framing, see Log returns.

Z: ≈ -9.4%/yr

OPEN: ≈ -138.9%/yr
Data alignment: No forward fill. Correlation and tail co-moves are computed on shared closes only.
For cross-calendar pairs (e.g., crypto vs stocks), weekend/holiday moves roll into the next shared close.
Return conventions: Volatility/Sharpe/Sortino use simple daily returns. Tail-risk uses daily log returns for distribution stats (but tables show simple returns). Log returns.

Formulas

Daily simple return

r_t = \frac{P_t}{P_{t-1}} - 1

Volatility

\sigma_{ann} = \sigma(r_t)\sqrt{A}

Volatility drag (approx.)

\text{drag} \approx \tfrac{1}{2}\sigma_{ann}^2

Sharpe Ratio

S = \frac{A\,\bar{r} - r_f}{\sigma(r_t)\sqrt{A}}

Sortino Ratio

So = \frac{A\,\bar{r} - r_f}{\sqrt{\mathbb{E}[\min(0,\,r_t - r_f/A)^2]}\,\sqrt{A}}

Maximum Drawdown

MDD = \min_t\left(\frac{P_t}{\max_{s \le t} P_s} - 1\right)

Average Correlation

\rho = \frac{\operatorname{cov}(r^A,\,r^B)}{\sigma_A\,\sigma_B}

Log returns

\ell_t = \ln\left(\frac{P_t}{P_{t-1}}\right)

Notation

$P_t$: Price on day t.
$r_t$: Simple daily return.
$\ell_t$: Log daily return.
$\bar{r}$: Average daily return.
$\sigma(r_t)$: Standard deviation of daily returns.
$A$: Annualization factor (days/year).
$r_f$: Annual risk-free rate.

Zillow vs Opendoor: Frequently Asked Questions

Which has higher volatility: Z or OPEN?

OPEN showed higher volatility at 166.7% annualized, compared to 43.3% for Z Over the past year. Higher volatility means larger price swings in both directions.

Does Z provide diversification when held with OPEN?

Z and OPEN are weakly correlated over the past year, with an average correlation of 0.22. This weak correlation suggests meaningful diversification benefits when held together.

How bad are the worst 5% days for Z vs OPEN?

Over the past year, Z's 5% VaR was -4.58% and its 5% Expected Shortfall was -6.67% (worst 13 days). OPEN's were -11.78% and -17.12% (worst 13 days).

Do Z and OPEN crash together on bad days?

On shared dates (n=249), when OPEN has a 2σ down day, Z also does 0.0% (0/3 days). In the other direction, when Z has one, OPEN also does 0.0% (0/6 days).

Which has better risk-adjusted returns: Z or OPEN?

Z had a negative Sharpe (-1.09) while OPEN was positive (1.48) Over the past year, indicating OPEN had meaningfully better risk-adjusted performance.

Can Z and OPEN be combined in a portfolio?

Yes, though allocation sizing matters. Their weak correlation could meaningfully reduce overall portfolio variance. OPEN's higher volatility (166.7%) means even small allocations can materially impact overall portfolio risk.