Every tracked symbol's weekly band, scored on the week's last close: measured coverage against the 68% theory, breaks that cluster in the same week, and differences by period, band width, group and symbol.
Operator: SilverPeak · Editorial: SigmaRange Published: · Updated: · Data through: close
69.7% of weeks finished inside the band. The week-clustered 95% interval (67.2%~72.3%) contains the normal-theory 68.3%, so the overall average is indistinguishable from theory. Breaks were more frequent upward (17.0%) than downward (13.2%). 5.9% finished beyond ±2σ against a theoretical 4.6%: large breaks were rarer than small ones but more common than a normal model says.
Closed inside
69.7%
theory 68.3%
At/above +1σ
17.0%
theory 15.9%
At/below −1σ
13.2%
theory 15.9%
Sample
19,355
185 symbols · 111 weeks
1. Theory against measurement
Measure
Measured
Normal theory
Inside ±1σ
69.7%
68.3%
At/above +1σ
17.0%
15.9%
At/below −1σ
13.2%
15.9%
Beyond ±1.5σ
13.6%
13.4%
Beyond ±2σ
5.9%
4.5%
On average the width the options market priced each week did not miss realized weekly closing moves by much. A close outside ±1σ happened 30.3% of the time, roughly once every 3 weeks. An average close to theory is not the same as that share holding every week; section 2 shows the difference.
2. Breaks arrive together
Of 111 weeks, 9 had fewer than half the names inside and 25 had 80% or more. The worst was the week closing 2025-04-04: 36 of 170 (21.2%) finished inside, with 134 at or below −1σ.
Week closing
Names
Inside
≥ +1σ
≤ −1σ
2025-04-04
170
21.2%
0.0%
78.8%
2024-09-06
166
30.1%
4.2%
65.7%
2026-10-16
184
33.2%
20.1%
46.7%
2025-05-16
171
42.7%
56.1%
1.2%
2024-09-13
166
45.2%
54.2%
0.6%
3. By period
Half-year
Weeks
Symbol-weeks
Inside
≥ +1σ
≤ −1σ
2024-H2
17
2,839
66.3%
19.0%
14.7%
2025-H1
26
4,423
68.0%
17.3%
14.7%
2025-H2
26
4,549
72.7%
17.2%
10.1%
2026-H1
26
4,664
69.3%
17.5%
13.2%
2026-H2
16
2,880
4. By band width
Weekly 1σ width
Symbol-weeks
Inside
≥ +1σ
≤ −1σ
±0.7–2.9%
3,852
69.1%
15.7%
15.3%
±3.0–3.9%
3,858
69.6%
16.7%
13.7%
±3.9–5.6%
3,893
69.3%
17.3%
13.4%
±5.6–9.4%
3,873
68.5%
18.1%
13.3%
±9.4% +
3,879
72.2%
17.2%
10.6%
Split into width quintiles, the inside share ran from 68.5% to 72.2%. Narrow-band and wide-band names finished inside at similar rates: the options market broadly scaled each name's width to its volatility, which is what lets different symbols share one σ scale. The widest bucket includes very wide bands on thinly traded options (up to ±371%).
5. By group
Group
Symbols
Symbol-weeks
Inside
≥ +1σ
≤ −1σ
Semiconductors
22
2,164
69.1%
18.7%
12.2%
Financials
14
1,548
69.8%
16.4%
13.8%
Healthcare
13
1,441
70.4%
16.6%
13.0%
Software
12
1,272
65.1%
19.2%
15.7%
Power
11
1,217
6. By symbol
The 177 symbols with at least 52 weeks range from 59.5% to 81.8% inside. With about 111 weeks each, identical odds would still spread them by roughly ±8.5 points. The observed spread (SD 4.6 points) is close to that chance level (4.4), so most of the ranking is sampling noise rather than a trait of the symbol.
Universe: the stocks and index ETFs on the board today plus the SPDR sector funds. Symbols dropped earlier are not included, so survivorship bias is possible.
Band: the prior week's last regular-session close as anchor, with that day's option-implied move converted to 1σ and held all week. Past weeks are restored from the option term structure of the time; weeks that used the time-scaling fallback are included.
Scoring: a last close above −1σ and below +1σ counts as inside; at or above +1σ as above; at or below −1σ as below. A week that broke intraday but closed back inside counts as inside.
Excluded: bands not confirmed from anchor-date data, weeks without a close on the band's last session, the week in progress, and symbols whose archive could not be read.
95% interval: names in the same week move together, so symbol-weeks are not treated as independent. Each week's inside share is one observation, with a normal approximation.
Updates: recomputed when a new weekly band starts. The revision date changes only when the text or method changes.
This run: 185 symbols, weeks closing 2024-09-06 to 2026-10-16, 19,355 symbol-weeks (2,135 on the time-scaling fallback).
This measures range coverage, not trading performance or directional forecasts. Whether a close outside the band predicts what follows is still under validation.
If you find an error in the numbers or method, contact us.
2024-11-08
168
47.0%
52.4%
0.6%
A market-wide shock pushes many names outside in the same direction in the same week. Treating 19,355 symbol-weeks as independent would understate uncertainty, so the 95% interval here uses each week's inside share as one observation (weekly mean 69.7%). When one symbol breaks on the board, check whether the rest of the board broke with it.
71.7%
13.7%
14.6%
By half-year the inside share ranged from 66.3% (2024-H2) to 72.7% (2025-H2). 2024-H2 and 2026-H2 cover fewer weeks and vary more. Any upward or downward skew may reflect the market regime of the period and is no basis for expecting it to persist.
71.4%
17.0%
11.6%
SPDR sector ETFs
11
1,188
70.9%
15.2%
14.0%
Benchmarks & ETF
11
1,126
68.8%
17.9%
13.2%
Industrials & Defense
10
1,105
69.0%
16.0%
15.0%
Consumer Discretionary
8
885
68.8%
14.8%
16.4%
Mega Cap
7
777
68.5%
19.0%
12.5%
Communication Services
7
775
70.1%
15.5%
14.5%
Optical
7
760
69.3%
19.5%
11.2%
Materials & Commodities
6
666
69.7%
20.0%
10.4%
Crypto
6
566
70.7%
16.1%
13.3%
Quantum
6
475
74.1%
14.7%
11.2%
Space
6
458
69.2%
18.3%
12.4%
Defensive
4
444
70.5%
15.8%
13.7%
Energy
4
440
67.0%
16.8%
16.1%
Neocloud
5
431
71.0%
17.2%
11.8%
China ADR
3
333
74.5%
13.5%
12.0%
Real Estate
3
331
77.0%
10.9%
12.1%
Materials
3
288
74.7%
12.8%
12.5%
Consumer Staples
2
222
73.4%
14.0%
12.6%
Technology
2
222
67.1%
20.7%
12.2%
Networking
2
221
66.1%
20.8%
13.1%
Among groups with five or more symbols, Quantum had the highest inside share (74.1%) and Software the lowest (65.1%). Small groups mostly reflect a handful of names, and members of one group move together in the same weeks, so do not generalize these gaps into sector traits.