Is It Really Worth Investing in the Stock Everyone Is Talking About?

Reading time 4 minutes

Published on 15/05/2026

The value reached by the world's largest listed companies, many of them US firms operating in the technology and artificial intelligence sectors, often attracts considerable media attention and can fuel excitement. Small investors, drawn to recent strong performance, may be tempted to make hurried investment decisions without fully considering the risks involved.

Today, more than ten companies are each valued at over one trillion US dollars on the stock exchange. Let us take a closer look at what these extraordinary valuations mean and why diversification remains one of the most important principles for anyone investing their money.

The value of a Listed Company

The market value of a listed company is known as its market capitalisation. It is calculated by multiplying the price of a single share by the total number of shares issued by the company.

At present, thirteen companies worldwide each have a market capitalisation exceeding one trillion US dollars. The seven largest are worth more than two trillion dollars each.

To put this into perspective, one trillion dollars is roughly equivalent to the combined value of all companies listed on the Italian stock exchange at the end of 2025, according to Consob data.

These figures are so large that even a 1 per cent change in the value of one of the biggest companies can amount to tens of billions of dollars - more than the entire market value of many major listed firms.

A truly Astronomical Valuation

Imagine taking part in the Artemis II space mission, travelling around the far side of the Moon and then returning to Earth. Now imagine that the entire route is lined with one-dollar banknotes placed end to end.

To reach one trillion dollars, you would need to travel that distance and count those banknotes more than 130 times.

The Winner Takes It All (Almost)

It is not unusual for successful companies to become very large. What is remarkable is just how much larger they have become in recent years.

A saver might reasonably ask: Should I have invested in these companies? Should I invest in them now?

There is no universally right answer. Investment decisions are personal and depend on each individual's circumstances, objectives and attitude towards risk. However, there are some basic principles that everyone should keep in mind.

One of them is avoiding hindsight bias - the tendency to believe that past events were predictable once we know the outcome. Looking back, the success of today's market leaders may seem obvious. In reality, nobody knows in advance which companies will be the winners of tomorrow. It would be imprudent to assume that a company will continue to generate exceptional returns simply because it has done so in recent years.

History provides many examples. A brief look at the largest listed company in the United States over time shows how leadership changes:

• In 1995, the largest company was General Electric;
• In 2005, it was Exxon Mobil;
• In 2015, Apple took the top position.

Every era has its leading companies. What about the future? No one knows. The world's largest company in ten years' time may be a business that is currently little known - or one that does not yet exist.

What Can a Small Investor do?

Warren Buffett once used an effective metaphor: "The weeds become less important as the flowers bloom."

In other words, a few highly successful investments can outweigh many disappointing ones.

The challenge is that when plants are still small, it is very difficult to tell the weeds from the flowers. Likewise, identifying in advance the companies whose value will grow dramatically is extremely difficult.

So what can investors do?

A straightforward answer is: diversify.

For example, investing through a fund or an ETF that tracks a market index allows investors to:

• spread their money across a wide range of investment opportunities;
• benefit from the growth of the broader market, ideally on a global scale;
• avoid relying on the performance of a single company or investment.

In Summary

Great success stories are easy to recognise in hindsight but extremely difficult to predict in advance.

For this reason, rather than chasing the stock of the moment, it may be wiser to adopt a diversified investment strategy. Spreading investments across different shares - including, if appropriate, the market's current favourites - and across different markets can help ensure that the value of your savings is not tied to the fortunes of a single company. At the same time, it allows you to participate in the growth of the wider economy.