When I turned to AI to answer the question in the title to this post, ChatGPT replied “Monaco,” as did Grok, while Gemini (Google) came back with “San Francisco.” Gemini, however, specified that it had surveyed only “major” cities. When asked to include all cities, it too indicated Monaco. AI provided different numbers when asked how many billionaires currently live in the small city (and country). Gemini and Grok replied “two,” while ChatGPT gave a much higher figure and a more nuanced answer: “most current estimates put the number of resident billionaires in Monaco at roughly 15–30 people/families, depending on methodology and whether family fortunes are counted individually.” Gemini and Grok also claim that Monaco has seen a decline in the number of its billionaires in recent years, whereas ChatGPT tells me that “Monaco appears to have remained stable or become even more attractive to ultra-wealthy residents since the early 2020s.”* Intriguing, several YouTube videos try to convince their viewers that the gilded little principality is currently in fast decline, being abandoned by its hyper-wealthy residents.
Given such disparate answers, all such assessments should be treated with skepticism. It may be impossible, moreover, to find sold answers to these questions, given the secrecy of many billionaires as well as their propensity to maintain homes in multiple places and frequently move from one to another.
I have, however, gained some insight into this issue by mapping the primary residences of the ultra-wealth, as can be seen in the previous two GeoCurrents post and another that is forthcoming. Thus far I have mapped only those with current fortunes above $6 billion. For this rarified category, Monaco is clearly not in the top position. It is instead occupied by either Ingelheim, Germany or Billund, Denmark. It is also possible that Monaco is surpassed by one or both of these cities when it comes to the class of all billionaires. Although Grok initially told me that Monaco has the highest per capita number, it changed its (non)mind when I provided more information and asked for an explicit comparison with Ingelheim. Here are its original and revised responses:
- Monaco: Data varies slightly by source (Forbes vs. Henley/New World Wealth), definition (city proper vs. metro), and residency rules (primary vs. secondary homes). Billionaires are mobile, so counts fluctuate. Monaco’s extreme concentration makes it the clear per-capita leader.
- Ingelheim. Its per capita rate is roughly 140–400+ billionaires per million residents(or about1 per 2,400–7,000 people), making it one of the highest in the world for a small town—far exceeding Monaco’s rate … “
In mapping the primary residences of the ultra-wealthy, I have been surprised by how many of them are aggregated in a few little-known cities. Such cases generally result from multiple family members sharing a massive inheritance and remaining primarily lodged in a city dominated by a single company that generated their wealth. A good example is the provincial Danish city of Billund (population 7,484), home of the Lego Group. Four persons with fortunes greater than six billion US dollars reportedly reside primarily in this modest town: Kjeld Kirk Kristiansen, Thomas Kirk Kristiansen, Sofie Kirk Kristiansen, and Agnete Kirk Thinggard. Billund might have the world’s highest per capita number of billionaires, with one per 1,871 residents.
Other than Monaco, Billund’s main rival for this dubious distinction is the small German city of Ingelheim am Rhein, with a population of roughly 36,000. Its case is particularly complicated. The Forbes tally of “real time billionaires” lists 15 individuals in a row with fortunes pegged at $6.5 billion, all of whom reside primarily in Ingelheim, at least according to Gemini (as of May 18, 2026; see the table below). Intriguingly, all 15 have the surnames of “Boehringer” or “von Baumbach.” But because these intertwined families are notoriously secretive, it is difficult to determine where their wealthiest members primarily reside or how large their fortunes actually are. It is not coincidental that no photographs are available for any of them in the segment of the Forbes list posted below. Grok AI summarizes the situation nicely:
Forbes and related analyses (e.g., mapping of German billionaires) indicate Ingelheim appears with a notable cluster [of billionaires]—potentially 5–15+ depending on how family members are counted individually vs. aggregated, as the company is privately held by the Boehringer, Liebrecht, and von Baumbach families with wealth split among ~15+ heirs in total.
Although Ingelheim is apparently home to more billionaires than Billund, it is a far less provincial city, making its concentration of extreme wealth less exceptional. The driving distance from Copenhagen to Billund is roughly 260 kilometers (160 miles), and the nearest substantial city, Aarhus, is approximately 90 kilometers distant. Ingelheim, on the other hand, is a mere 46 kilometers (29 miles) from Frankfurt (straight-line distance) and only 14.6 kilometers (9.1 miles) from Mainz, a city of more than 200,000 residents. Put differently, it is squarely situated in the Rhine-Main Metropolitan Region, a conurbation with almost six million inhabitants – and quite a few additional billionaires.
The source of the Ingelheim’s vast private wealth is C.H. Boehringer Sohn AG & Co. KG, the parent company of the Boehringer Ingelheim group. Boehringer Ingelheim is the world’s largest privately held pharmaceutical firm, with 54,000 employees in 76 countries. Founded by Albert Boehringer in 1885, the company is still owned by his descendants, now in the fourth generation.
I am embarrassed to admit that I had never heard of this important company before I began working on this project. Judging from what I have read (and watched), Boehringer Ingelheim had a decidedly mixed reputation. Often praised for its long-term planning and dedication to cutting-edge research, it is also criticized for its intense secrecy. The company has also been faulted for its history of close cooperation with the German Empire (1871-1918) and the Nazi regime (1933-1945). Such criticism is perhaps unfair, as the company had little choice but to work with these authoritarian regimes. It is a different matter, however, when it came to the hiring of Fritz Ernst Fischer in 1954. As noted in Fischer’s Wikipedia article:
Fritz Ernst Fischer (1912-2003) was a Nazi German medical doctor who performed medical atrocities on inmates of the Ravensbrück concentration camp. He was tried and convicted of war crimes and crimes against humanity in the 1947 Doctors’ Trial; he was sentenced to life imprisonment, but his sentence was commuted to 15 years and he was released in 1954. … Fischer subsequently regained his license to practice medicine and started a new career at the chemical company Boehringer in Ingelheim, where he stayed until his retirement:
*These answers came in response to being asked where the number of billionaires living in Monaco has decreased in recent years.