Why So Many Buildings Skip the 13th Floor: The Real History and Data Behind Triskaidekaphobia

Walk into almost any American high-rise and press the elevator button for the 13th floor, and there's a good chance it simply doesn't exist — at least not by that name. The numbers jump from 12 straight to 14, or the missing floor gets relabeled 12A, M for mechanical, or something else entirely. This is not an urban legend or a rare curiosity; it is a well-documented, still-common practice in real estate and architecture, backed by actual industry surveys. But the fear behind it, known formally as triskaidekaphobia, has a much messier history than most retellings suggest — a tangle of biblical tradition, Norse mythology, numeral systems, and nineteenth-century storytelling, much of which is disputed or unverifiable rather than settled fact. This essay separates what is actually documented — building surveys, academic studies on Friday the 13th, and dated etymology — from the folklore that gets repeated as if it were history.

The most frequently cited statistic on this topic comes from Otis Elevator Company, the elevator manufacturer whose cars carry people up and down buildings around the world and whose service records give it an unusually good vantage point on how floors are actually labeled. In data reported in the early 2000s, an Otis representative, Dilip Rangnekar, stated that approximately 85 percent of buildings serviced by Otis elevators with 13 or more floors did not have a floor labeled the 13th — instead using renumbering, letter designations, or reserving the space for mechanical equipment. This figure has been repeated widely in outlets covering the topic, including the Skeptical Inquirer's reporting on superstition and real estate.

A more geographically specific data point comes from a 2015 analysis of New York City condominium buildings, cited in the Skeptical Inquirer's coverage of the subject: out of 629 Manhattan condo buildings with 13 or more stories, roughly 91 percent omitted a floor explicitly labeled 13. That kind of concentration in a single, densely built market suggests the practice isn't a scattered quirk but something closer to an industry default, at least in high-rise residential and commercial construction.

Consumer attitudes back up why builders bother. A 2007 Gallup poll found that about 13 percent of American adults said they would be bothered by being assigned a hotel room on the 13th floor, and 9 percent said they would request a room change if that happened. That's a real, if modest, share of the market — enough to matter to a hotel chain or condo developer weighing the near-zero cost of skipping a number against a small but nonzero group of buyers or guests who might balk.

There is also research suggesting the superstition can carry a real, if resistible, price effect. Economists Nikolai Antipov and Nadia Pokryshevskaya studied Russian apartment sales and found that units on 13th floors sold for less and moved more slowly than comparable units — an effect that could be erased entirely by a price discount of roughly 10 percent or more, according to their analysis, meaning the superstition functions less as an absolute barrier than as something buyers will trade away for a big enough discount.

Not every market or developer plays along. Toll Brothers, a major U.S. homebuilder, has stated it builds Manhattan towers with numbered 13th floors and considers the superstition unfounded, and the Miami-based real estate investment firm 13th Floor Investments has built the number directly into its brand identity. The city of Vancouver, meanwhile, went the opposite direction from a public-safety angle: its planning rules prohibit skipping floor numbers like 4 and 13 specifically so that firefighters and other emergency responders are never confused about which physical floor they're standing on when a building's numbering doesn't match its actual floor count.

One of the oldest and most persistent explanations for the number 13's bad reputation is mathematical and calendrical rather than religious: the ancient Sumerians used a base-12 (duodecimal) counting system, and the number 12 became embedded across cultures as a marker of completeness — 12 months in a year, 12 hours on a clock face, 12 signs of the zodiac, 12 Olympian gods in Greek mythology, 12 tribes of Israel, 12 apostles. Historians and mathematicians note that against this backdrop, 13 appears as the number that comes after completeness — a disruption of a tidy, culturally reinforced pattern, which may partly explain why it was primed to be read as ominous once other, later associations attached themselves to it.

A frequently repeated but debunked claim involves the Code of Hammurabi, the ancient Babylonian legal text, which some retellings say deliberately omitted a 13th law out of superstition. Historians who have examined this claim, including reporting summarized by History.com, describe it as false: the original Babylonian code was not actually numbered by its ancient authors at all, and the appearance of a 'missing' 13th law traces to a clerical or translation error introduced by a much later translator numbering the laws for modern readers. It's a useful cautionary example of how a factoid can circulate as ancient history when it is, in fact, a modern accident.

The most commonly cited religious origin is the Last Supper: at the meal before his crucifixion, Jesus dined with his 12 apostles, making 13 people at the table, and Judas Iscariot — the apostle who would betray him — is frequently described as the 13th guest to arrive or the last to be seated. It's worth being precise about what's actually documented here: the Gospel accounts describe 13 people present but do not specify a seating order or single out Judas as literally 'the 13th' in any numbered sense. That detail appears to be a later narrative embellishment layered onto the biblical account rather than something stated in scripture itself.

A related and independently documented superstition is the 'thirteen at a table' belief — the idea that if 13 people sit down to dine together, one of them will die within the year. This belief is traceable in written sources back to at least 1774, according to research summarized in reference works on the topic, and the German scholar Johann August Ephraim Götze is credited with an early theory tying it to the Gospel narrative of the Last Supper. Whether the Last Supper story generated the dinner-table superstition, or whether an existing folk superstition got retroactively attached to the biblical scene, is exactly the kind of question historians treat as genuinely unresolved rather than settled.

Alongside the Last Supper, the second origin story most often cited for the number 13's bad luck comes from Norse mythology: the tale of Loki, the trickster god, allegedly crashing a banquet in Valhalla as an uninvited 13th guest, an intrusion that leads to the death of Baldr, the god of light and joy, plunging the world into darkness and grief. This story is genuinely old and genuinely part of the Norse mythological corpus — the death of Baldr, engineered by Loki's trickery involving a mistletoe dart, is a real and significant episode in the Prose Edda, the medieval Icelandic text that is a primary source for Norse mythology.

But readers should treat the specific '13th guest at a dinner party' framing with real caution. As reference summaries of the myth point out, the original Prose Edda source material does not itself emphasize the number 13 or frame the event explicitly as a dinner party with a numbered guest list; that specific retelling — count of guests, banquet setting and all — appears to be a modern popularization, notably associated with 20th-century mythology writers like Douglas Hill, rather than a detail preserved in the medieval source text itself. In other words: Baldr's death by Loki's hand is real Norse myth; the tidy '13th guest' arithmetic wrapped around it is very likely a later literary flourish, not an ancient detail.

This distinction matters for anyone trying to write or read honestly about the topic. Popular articles routinely present the Norse story and the Last Supper story side by side as if both were equally well-attested ancient explanations for fear of 13. In reality, both are best described as origin legends that entered wide circulation well after the fact — useful and evocative as cultural artifacts, but not verifiable as the actual historical root of triskaidekaphobia in the way, say, a dated etymology or a Gallup survey is verifiable.

What can be said with more confidence is that by the 19th century, multiple independent unlucky-13 traditions — the dinner-table superstition, the Judas association, the general cultural discomfort with breaking the pattern of 12 — were circulating in Western Europe and North America, feeding into and reinforcing one another, and that by the time triskaidekaphobia was named as a clinical-sounding phobia, it already had centuries of accumulated, mutually reinforcing folklore behind it rather than a single clean point of origin.

The word triskaidekaphobia is built from Ancient Greek: treiskaideka, meaning thirteen, and phobos, meaning fear. Etymological references, including Etymonline and Merriam-Webster, date its first documented use in English to right around 1910–1911. Wikipedia's sourcing attributes an early documented appearance of the term in professional literature to psychiatrist Isador Coriat's 1910 book Abnormal Psychology, which places the coining of the clinical-sounding label squarely in the early 20th century — considerably more recent than the folklore it describes.

That timing is itself informative: the fear of 13 clearly predates the word for it by a long stretch, but giving it a formal Greek-derived phobia name around 1910 coincides with a broader cultural moment when psychology was professionalizing and cataloguing named phobias, and when American popular culture — magazines, early self-help writers, and later pulp fiction — was actively retelling and dramatizing 13-related superstitions for mass audiences.

Modern estimates of how many people are affected vary by source and methodology, but National Geographic's reporting on the subject cites estimates that triskaidekaphobia affects somewhere between 17 and 21 million people in the United States, with symptoms ranging from mild unease to anxiety severe enough that some sufferers avoid travel, business, or even leaving the house on days associated with the number.

A closely related but distinct term is paraskevidekatriaphobia, specifically the fear of Friday the 13th (from the Greek for Friday, paraskeví, plus dekatria for thirteen). The two fears are often conflated in casual usage, but triskaidekaphobia is the broader fear of the number 13 in any context — an elevator panel, a hotel room key, a house number — while the Friday-specific version narrows in on the particular calendar combination discussed in the next section.

Friday the 13th is where the folklore and the peer-reviewed literature collide most directly, and the honest answer is that the science is mixed rather than conclusive. The most frequently cited study is a short 1993 paper in the British Medical Journal by Scanlon, Luben, Scanlon, and Singleton, which compared traffic patterns and hospital admissions in London's South West Thames region on a Friday the 13th versus the preceding Friday the 6th. The researchers found significantly fewer vehicles on the road on Friday the 13th, suggesting some people avoided driving — yet transport-accident hospital admissions were still significantly higher that day (65 versus 45 admissions, a statistically significant difference), leading the authors to a wry conclusion that the risk of a road-accident hospital admission may rise by as much as 52 percent on Friday the 13th, and that staying home might be the safer option.

That finding does not stand unchallenged, however. A 2002 study by Finnish researcher Simo Näyhä, published in the American Journal of Psychiatry, analyzed Finnish traffic fatality data over several decades and reported an elevated risk of traffic deaths on Friday the 13th, particularly among women. But a 2004 study published in BMC Public Health, titled 'Females do not have more injury road accidents on Friday the 13th,' revisited similar territory using different data and explicitly contradicted that specific finding, reporting no significant increase in road injury accidents among women on the date in question. Taken together, these studies are a textbook example of an area where results diverge depending on the country, time period, and methodology used — which is exactly why researchers in this space describe the overall 'Friday the 13th effect' on accidents as unsettled rather than proven.

A similar pattern shows up in finance. A well-known 1987 paper by economists Robert Kolb and Ricardo Rodriguez, published in The Journal of Finance under the title 'Friday the Thirteenth: Part VII — A Note,' reported that average U.S. stock market returns on Friday the 13th were historically, statistically significantly lower than returns on other Fridays — a provocative finding that got wide attention. Subsequent researchers have revisited the claim with more recent data and different markets, including studies looking at emerging Asian markets and the Indian stock market, with results that have been decidedly mixed: some later analyses failed to replicate a robust or lasting 'Friday the 13th effect' once more data and more rigorous statistical controls were applied, and the original Kolb and Rodriguez finding is widely treated in behavioral finance literature today as a famous but contested result rather than settled market law.

Beyond accidents and stock returns, oft-repeated figures about the economic cost of Friday the 13th — commonly cited in the $800 million to $900 million range in lost business from people avoiding flying, shopping, or other normal activities, a figure that appears in National Geographic's reporting and elsewhere — should be read as informal, hard-to-verify industry estimates rather than figures backed by a specific, citable economic study. They circulate widely, but readers should treat them the way they'd treat any unattributed 'industry estimate': plausible in direction, but not rigorously sourced.

The overall, fair scientific summary is this: there is real, peer-reviewed research asking whether Friday the 13th correlates with more accidents or worse market returns, and at least some studies have found statistically significant effects in specific datasets — but other studies looking at similar questions with different data have found no such effect, and no consistent, replicated pattern has emerged across countries and time periods. That mixed, sometimes-contradictory record is itself the honest finding, and is very different from confidently asserting that Friday the 13th is 'proven' unlucky.

The missing-13th-floor phenomenon has close cousins throughout the travel and hospitality industries. Reporting from outlets like Simple Flying documents a long list of airlines that omit row 13 from their seating charts entirely, including Iberia, Lufthansa, Air France, Ryanair, Virgin Atlantic, Emirates, Qatar Airways, and several Asian carriers such as Cathay Pacific and Thai Airways, along with United Airlines on most of its aircraft. Notably, some carriers skip different numbers for different regional superstitions in the same fleet: Lufthansa also omits row 17 (unlucky in Italy), while Cathay Pacific and Hong Kong Airlines skip row 14, because in Cantonese and Mandarin the pronunciation of 14 can sound close to a phrase associated with death — a reminder that 'unlucky numbers' are culturally specific rather than universal. Hospitals and hotels commonly follow the same logic as office towers, frequently omitting a labeled room or bed 13, though this is a matter of institutional custom and public documentation rather than a single verifiable industry-wide count.

The clearest illustration that fear of 13 is a Western, and specifically largely Christian-cultural, phenomenon rather than a human universal comes from Italy, where 13 is not the primary unlucky number at all — 17 is. As explained in reporting from outlets covering Italian folklore, the number 17 written in Roman numerals as XVII can be rearranged as an anagram of VIXI, Latin for 'I have lived,' a funerary phrase historically associated with the dead, which is the most commonly cited explanation for its unlucky status in Italian tradition. Interestingly, 13 has a mildly positive association in some Italian contexts — the phrase 'fare tredici,' or 'to make thirteen,' traditionally refers to winning big (from a old football pools game requiring 13 correct predictions), illustrating that the same number can carry opposite cultural valence depending on where you are.

Other cultures fear entirely different numbers for their own linguistic or symbolic reasons. In China, Japan, and other East Asian cultures, the number 4 is widely avoided because its pronunciation in Mandarin (si) and other regional languages closely resembles the word for 'death' — leading many East Asian buildings, hospitals, and hotels to skip labeled 4th floors, room numbers containing 4, or license plates ending in 4, in a pattern strikingly parallel to Western avoidance of 13. Ancient Egyptian tradition, by contrast, is sometimes cited as having actually regarded 13 as a positive number, associated with the ascent to eternal life in their conception of the afterlife's stages — a data point frequently used to argue that fear of 13 is a cultural artifact rather than some innate human reaction to the number itself.

Named, real-world examples of how developers navigate this today include Boston's Millennium Tower, a 2017-opened luxury residential skyscraper that omitted both its 13th floor and its 44th floor — the latter a nod to East Asian numerological concerns about 4, given the building's international buyer base. That kind of dual accommodation, addressing both Western superstition about 13 and Asian superstition about 4 in the same building, is a small but telling piece of evidence that modern developers treat these avoidances as pragmatic marketing decisions rather than personal beliefs — a nearly costless way to avoid alienating any segment of superstitious buyers, whatever number they happen to be wary of.

• Why Is 13 Unlucky? | Britannica
• Triskaidekaphobia — Wikipedia
• Afraid of the Thirteenth Floor? Superstition and Real Estate, Part 2 — Skeptical Inquirer
• What's So Unlucky About the Number 13? — History.com
• Friday the 13th Superstitions Rooted in Bible and More — National Geographic
• Is Friday the 13th bad for your health? — Scanlon et al., BMJ 1993 (PubMed)
• Traffic Deaths and Superstition on Friday the 13th — Näyhä, American Journal of Psychiatry (2002)
• Females do not have more injury road accidents on Friday the 13th — BMC Public Health (PMC)
• Friday the Thirteenth: 'Part VII' — A Note — Kolb & Rodriguez, The Journal of Finance (1987)
• Why Most Airlines Don't Have A Row 13 On Their Planes — Simple Flying
• Why 17, Not 13, Is Considered Unlucky In Italy — Grunge
• Triskaidekaphobia — Merriam-Webster