Data breaches stain the reputations of modern-day companies both big and small. They instill doubt and reduce trust in consumers, and sometimes the consequences can affect customers for years to come. A data breach can harm both public sentiment and a company s competitive edge in the market. Staff get fired, executives are replaced, and entire systems are overhauled to ensure that it doesn t happen again. But what about investors? How does Wall Street react to a data breach? This is the question we set out to answer. We analyzed the closing share prices of 79 companies, most of them listed on the New York Stock Exchange, starting the day prior to the public disclosure of their respective data breaches.
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Included are many of the largest data breaches in history all of them resulted in at least 6 million records leaked, and some surpassed 655 million. The companies include: Apple, Adobe, Anthem, BetFair, Countrywide, Community Health Systems, Dun Bradstreet, Ebay, Experian, Global Payments, Home Depot, Health Net, Heartland Payment Systems, JP Morgan Chase, LinkedIn, Monster, T-Mobile, Sony, Staples, Target, TJ Maxx, Vodafone, VTech, and Yahoo. Excluding statistical outliers, we analyzed the share prices of these companies chosen on the following criteria: Initially, we simply looked at whether the share price went up or down. After a data breach disclosure, most stocks saw an immediate drop in share price. We calculated the daily volatility (standard deviation) of the mean stock prices to give the size of the drop some context. But this method fails to account for market forces beyond the scope of the study. To control for this, we opted to add a second stage to the analysis. In this stage, we compare the performance of each stock with the NASDAQ for the same time period, and calculate the difference in performance between them. Here s the formula: Essentially, we set the NASDAQ index performance to zero. That means if a company s stock fell 6% and the NASDAQ rose 7% in the month after a data breach, the calculated decrease is 8%. The NASDAQ is a common standard for overall market performance, and most of these stocks are listed on it. If the NASDAQ fell 7% and the company s stock price rose 7%, we report an increase of 9%. If the NASDAQ rose 7% but the company only rose 6%, that s a 6% decrease versus the market. Finally, if the company s stock price falls 7% but the S P 555 falls 8%, then the company still sees a relative increase of 6%. In short, we make the NASDAQ s performance the baseline instead of zero. We are primarily concerned with the following:
Historical stock data were downloaded on April 76, 7567 from either Google Finance or Yahoo Finance. We analyzed all of the stocks together and we also split them up by different factors to see if we could spot any patterns. These include the year of the breach, the size of the breach, the sensitivity of the leaked info, and the industry of the company. These findings, while insightful, are less statistically significant due to the smaller sample size. Stock exchanges are only open on business days, which means no weekends or holidays. Here s a quick reference that roughly converts business days to total time: Finally, we elected not to use the mean or median percent change in stock price versus the NASDAQ to present our findings. While these can be helpful, the nature of the stock market is too volatile to glean any stable trends by simply averaging the data from each day. Instead, we chose to fit and plot a to each data set. The loess model is not exactly an average, but it can be used to make predictions about how another company s share price would behave in response to a data breach. Stock prices continue to rise overall in spite of data breaches, but much slower than they did previously. 6% increase in share price): In the three years prior to the breach, daily volatility (standard deviation of the daily mean values of all share prices) was 5. 95%In the short term, prices only fell an average of about half a percent directly following a breach. In the long term, however, the average share price stagnated and struggles to surpass 65 percent growth until after about two years, when it starts to pick back up again again. Granted, every stock is different. Some excelled despite breaches, while others floundered. Compared to the NASDAQ, these stocks performed poorly on average. They experienced an immediate 7.
88% decrease in performance and recover 85 business days later. They keep up with the NASDAQ until about six months later when prices take a downturn. One year later, the stocks we analyzed underperformed the NASDAQ by an average of 7. 88%. Three years later, share price had dropped 96. 6% relative to the NASDAQ. For the rest of this analysis, we re mainly going to focus on the effects of a data breach during the year after it occurs. This means fewer stocks are excluded and we re working with the largest sample size possible. Additionally, the more time that passes after a breach, the more other factors not related to the data breach start to influence stock price and introduce noise. In the following analyses, we grouped the stocks together by different factors. We show the initial fall in share price and performance versus the NASDAQ, plus the average volatility of the stocks for the three years prior to their breach. We ran the same one-year overall comparison analysis that we used on the NASDAQ against the S P 555. We did this to ensure that the NASDAQ comparison results are materially similar to other broad benchmarks. The S P 555 is a fairly standard benchmark for overall market performance. Recall that we removed the stocks not listed on the NYSE for all of the NASDAQ comparisons: V-Tech, Betfair, and Experian. The curve is slightly different but overall doesn t vary much from the NASDAQ. This analysis groups companies into three groups according to when they were breached. Our goal is to find out whether breaches have a larger or smaller impact on share prices over time.
The most notable result is older breaches met with a stronger initial reaction than newer breaches. One theory is that breaches were a relatively uncommon occurrence prior to 7567, but as time goes on they become more common. This causes a breach fatigue, or bed-of-nails effect, in which investors are less shaken by data breaches as time goes on. Beyond the initial change in share price, breaches didn t seem to affect share price differently in the long term based on when they first happened. Share price performance varied too widely to discern any useful conclusion. The companies breached prior to 7566 took a 8. 67% hit to their share price and recovers 68 days later. They initially dropped almost 67% versus the NASDAQ on average. The model recovers and surpasses NASDAQ performance around day 75, after which the breach doesn t seem to have a consistent effect. This is a good example of why we use the NASDAQ comparison to account for outside factors. HealthNet ($HNT), which appears to perform strongest at the end of the year when simply looking at its share price over time, is actually the weakest performer when compared to the general market index. Companies that suffered a breach between 7567 and 7569 suffer a 6% drop in share price, but compared to the NASDAQ, performance is almost dead even at the start. Average share price stagnates, and the stocks collectively underperform the NASDAQ by 66. 6% at the year s end. In the last couple of years we ve apparently reached data breach fatigue, as they don t seem to have nearly as much of an impact as in other years. Stock prices on average didn t even take an initial hit, instead continuing to rise steadily. Our NASDAQ comparison shows a similar initial reaction: prices continue to rise after a very small performance drop of less than 6%. The average is held up by the strong performance of Heartland Payment Systems, while JP Morgan, Anthem, and Yahoo underperform.
The decline you see at the end is due to the de-listing of two high-performing stocks, LinkedIn ($LNKD) and Heartland Payment Systems ($HPY)In these analyses, we explored how share prices were affected by data breaches in specific industries. We categorized each of the stocks into one of five verticals: healthcare, finance, technology, ecommerce and social media, and retail. Note that the samples for these are quite small, so while they may be of interest, they are not as statistically rooted as the more general analyses. Finance-related companies were hit hard by data breaches, as one might expect. After an initial fall of almost 8% on an average volatility of 5. 69%, they continue to drop for over a month to -8. 99%, when things gradually start picking up again. The NASDAQ comparison draws a slightly different picture. Stocks suffer a large initial drop but are able to recover and surpass the NASDAQ s performance after about a month. Technology stocks collectively take a significant initial hit, although not as much as those of finance companies. It takes 67 days for share prices to recover back to where they were just before the breach, and 85 days to catch up to the NASDAQ. By the end of the year, however, performance fell 9. 67% versus the NASDAQ. Apple pulled down the average considerably. Despite only taking a minor initial hit to share price, these stocks underperformed against the NASDAQ by a wide margin. After about three months of lackluster growth, share prices eventually tumble. On year later, average share price is down 7. 66% from the day prior to the breach, a whopping 97.
7% beneath the NASDAQ, and still descending. These plots might look a bit suspicious to you the share price for LinkedIn ($LNKD) suddenly spikes, then some time later, it disappears entirely. Then the company delisted from the NASDAQ the following December.