A market worth trillions of dollars – outside the stock exchange
There is a common misconception among investors: that the best companies are only traded on the stock exchange. In reality, many of the world's most valuable and fastest-growing companies sit outside the public markets. In the US there are over 1,200 private companies with a valuation of at least $1 billion, and their combined value exceeds $5 trillion. The five largest – OpenAI, SpaceX, Anthropic, Stripe and ByteDance – alone have a combined value of several trillion dollars.
This means that a large part of the technological innovation and growth shaping our future is happening among companies the average investor has no access to. At least that has been the case – until the secondary market for unlisted shares began to grow in earnest.
Why do companies stay private for so long?
The trend of staying private longer has accelerated markedly over the past decade. There are several interacting factors behind this. The first is that the private market now offers enough capital. OpenAI, for example, has raised over $58 billion in equity without needing to go public. SpaceX has raised roughly $12 billion in primary funding since its founding in 2002.
The second factor is freedom. A listed company lives under the tyranny of quarterly reporting – every three-month period, revenue must grow, margins must improve and expectations must be beaten. A private company can instead focus on building for the long term, even if that means periods of high costs and low profitability. OpenAI burned an estimated $8.5 billion during 2025 – something that would have caused panic among stock-market analysts, but which its private investors accept as a necessary investment in future growth.
The third factor is that the secondary market gives employees and early investors the chance to sell their shares without the company having to go public. This solves the classic problem that holdings in private companies used to be completely illiquid.
What is the secondary market and how does it work?
The secondary market for unlisted shares is a market where existing shareholders – employees, founders, early investors – can sell their shares to new buyers. This differs from new share issues, where the company itself issues new shares and raises capital.
In practical terms, a player like Accumeo matches buyers and sellers, verifies that the shares are transferable, handles the legal documents and carries out the transaction. Historically, this type of deal required personal networks, lawyers and very manual processes. Digital platforms have made the process considerably more accessible.
It is important to understand that pricing on the secondary market differs from the stock exchange. There is no continuous price updated every second. Instead, prices are based on the most recent completed transactions, ongoing negotiations and supply and demand.
Which companies can you invest in?
Accumeo focuses on the ten largest private companies in the US. These are companies in an entirely different size class than typical Swedish private companies. Here are some of the most prominent:
SpaceX has a valuation of around $1.4 trillion (February 2026) and generated an estimated $15–16 billion in revenue during 2025. Starlink, the company's satellite internet service, passed 10 million subscribers in February 2026 and accounted for the majority of revenue. The company reported operating earnings (EBITDA) of $8 billion in 2025.
OpenAI reported annual recurring revenue (ARR) of over $20 billion at the end of 2025, a tripling from $6 billion in 2024. ChatGPT had over 800 million weekly users and more than one million companies paid for the company's services. The valuation is estimated at around $500 billion.
Stripe processed $1.4 trillion in payments during 2024, up 38 percent year on year. Net revenue amounted to an estimated $5.1 billion in 2024 and the company is profitable. Half of the 100 largest listed companies in the US and 78 percent of the Forbes AI 50 list use Stripe. The valuation reached $107 billion in September 2025.
What sets this apart from investing in Swedish private companies?
The Swedish market for private companies is dominated by smaller growth companies – often at early stages with limited revenue and unproven business models. It is a market with high risk and potentially high returns, but also great uncertainty.
The American private companies that Accumeo offers are in a fundamentally different position. SpaceX has billions in revenue and is profitable. Stripe processes payments equivalent to 1.3 percent of the world's GDP. OpenAI has hundreds of millions of active users. These are not start-ups looking for their first customer – they are market leaders that have simply not yet chosen to go public.
That does not mean the risk is non-existent. Unlisted shares always have limited liquidity, lower access to information and uncertain valuations. But the nature of the risk is different compared with investing in a company with 70 employees.
Risks you should understand before investing
There are several risks specific to investing in unlisted shares, and they should not be underestimated.
Liquidity risk: You cannot sell your shares at any time. The secondary market is not an exchange with continuous trading. It can take time to find a buyer, and you may have to accept a lower price than you would like.
Valuation risk: Valuations on the secondary market are based on the latest transactions and can fluctuate sharply.
Information risk: Private companies are not required to publish financial reports the way listed companies are. You have access to less information and must rely more on estimates and analyses.
Lock-in risk: Some unlisted shares have transfer restrictions, for example requiring the company's approval for a sale. It is important to understand the terms before you buy.
How to get started with Accumeo
Accumeo is a platform that gives Swedish investors access to unlisted shares in the largest American companies. Via the platform you can explore which investment opportunities are available, review company information and complete purchases digitally.
It is wise to start by getting to know the companies you are interested in, understanding your own risk tolerance and deciding how large a share of your portfolio you want to allocate to unlisted shares. A common rule of thumb among professional investors is to keep the share of private assets to no more than 10–20 percent of the total portfolio.
