Equifax
Equifax disclosed unauthorized access involving sensitive identity information for roughly 143 million US consumers at the initial announcement.
-22.0% EFX vs +3.5% SPY
This site shows how share prices moved after an incident became public. It does not prove that the incident caused the move. Company news, sector moves and the wider market can affect every result. Educational only — not investment advice.
Disclosure timing
When could the market react?
The baseline is the last adjusted close before the news was public. The reaction session is the first close afterward.
- 01Baseline sessionSep 7, 2017
Normalized to 100 for both EFX and SPY.
- 02Public disclosureSep 7, 2017, 4:30 PM EDT
Documented publication time.
- 03First reaction closeSep 8, 2017
-13.7% company total return versus -0.1% for SPY; -13.5 pp market-relative return.
Time windows
Company vs SPY
Each row uses the last trading session on or before its target date. “Market-relative” is the company return minus the SPY return, in percentage points.
| Window | Endpoint | EFX | SPY | Market-relative | Signal |
|---|---|---|---|---|---|
| First reaction | Sep 8, 2017 | -13.7% | -0.1% | -13.5 pp | Below SPY |
| +7 days | Sep 14, 2017 | -32.3% | +1.3% | -33.6 pp | Below SPY |
| +1 month | Oct 6, 2017 | -22.0% | +3.5% | -25.5 pp | Below SPY |
| +3 months | Dec 7, 2017 | -17.9% | +7.5% | -25.3 pp | Below SPY |
| +6 months | Mar 7, 2018 | -14.8% | +11.6% | -26.4 pp | Below SPY |
| +12 months | Sep 7, 2018 | -3.5% | +18.7% | -22.2 pp | Below SPY |
Compare with current catalog aggregates
| Window | This case | Catalog median | Catalog mean | n |
|---|---|---|---|---|
| First reaction | -13.5 pp | -0.8 pp | -1.5 pp | 30 |
| +7 days | -33.6 pp | -2.0 pp | -4.0 pp | 30 |
| +1 month | -25.5 pp | -6.6 pp | -6.8 pp | 30 |
| +3 months | -25.3 pp | -5.1 pp | -6.6 pp | 30 |
| +6 months | -26.4 pp | -5.6 pp | -7.5 pp | 30 |
| +12 months | -22.2 pp | -3.7 pp | -10.1 pp | 30 |
Normalized total return
EFX compared with SPY
Baseline session = 100. Adjusted close reflects splits and reinvested distributions.
Equifax had -3.5% company total return versus +18.7% for SPY; -22.2 pp market-relative return. The chart shows normalized adjusted-close performance for up to 24 months.
View tabular chart fallback
| Date | EFX | SPY |
|---|---|---|
| Sep 7, 2017 | 100.0 | 100.0 |
| Oct 6, 2017 | 78.0 | 103.5 |
| Nov 6, 2017 | 75.7 | 105.4 |
| Dec 6, 2017 | 81.3 | 107.2 |
| Jan 8, 2018 | 85.8 | 112.1 |
| Feb 7, 2018 | 82.7 | 109.5 |
| Mar 9, 2018 | 88.1 | 114.1 |
| Apr 10, 2018 | 83.2 | 108.9 |
| May 9, 2018 | 80.3 | 110.7 |
| Jun 8, 2018 | 90.5 | 114.3 |
| Jul 10, 2018 | 91.0 | 115.1 |
| Aug 8, 2018 | 90.2 | 117.8 |
| Sep 7, 2018 | 96.5 | 118.7 |
| Oct 8, 2018 | 90.5 | 119.3 |
| Nov 6, 2018 | 73.5 | 114.0 |
| Dec 7, 2018 | 70.8 | 109.3 |
| Jan 9, 2019 | 68.4 | 107.6 |
| Feb 8, 2019 | 76.2 | 112.8 |
| Mar 12, 2019 | 79.5 | 116.5 |
| Apr 10, 2019 | 88.1 | 120.7 |
| May 10, 2019 | 85.4 | 120.6 |
| Jun 11, 2019 | 92.3 | 121.0 |
| Jul 11, 2019 | 98.1 | 126.0 |
| Aug 9, 2019 | 101.7 | 122.7 |
| Sep 6, 2019 | 105.6 | 125.4 |
Price recovery
Recovered
Here, recovery only means that adjusted close reached the baseline again. It does not mean every effect of the incident ended.
- State
- Recovered
- Initial trough
- -32.3% on Sep 14, 2017
- Recovery close
- Jul 23, 2019
- Calendar days
- 684
- Observation cap
- 24 months after disclosure
Hypothetical $1,000
What would $1,000 have looked like?
Compare $1,000 in EFX with $1,000 in SPY, bought and measured on the same dates.
Entry Sep 11, 2017 Exit Mar 9, 2018
Uses fractional shares and adjusted close. Leaves out taxes, fees and slippage. The holding period starts on the purchase date. This is a historical illustration, not an investment strategy.
Case note
Equifax said attackers exploited a web-application vulnerability and accessed names, Social Security numbers, birth dates, addresses and other data. The initial estimate covered approximately 143 million US consumers and was later revised.
The release was timestamped 4:30 p.m. EDT, after the regular session. Under the methodology, September 7 remains the baseline and September 8 is the reaction session—a material correction to the date-only treatment in the MVP.
Evidence
Sources and case review
We qualify each case before checking its price results. These links support the disclosure date, listing, incident and business impact.
- primary Sep 7, 2017Equifax announces cybersecurity incident involving consumer information Equifax Inc. Supports: Disclosure, Timing, Listing, Impact, Description
- Listing evidenceChecked Jul 20, 2026Equifax announces cybersecurity incident Equifax Inc. The issuer release identifies Equifax as NYSE: EFX and records a 4:30 p.m. EDT release time.
Why it is included. Equifax was the direct victim, published a timestamped announcement after market close, quantified the sensitive consumer exposure and later recorded substantial financial and regulatory consequences. Reviewed Jul 20, 2026.