They are just five companies but they are together worth more than the huge international businesses that make up the entire FTSE 100, more than the companies that comprise Hong Kong’s Hang Seng index, and more than Germany’s Dax and France’s Cac 40 put together.

They are the US technology giants collectively known as Faangs – Facebook, Amazon, Apple, Netflix and Google (owned by Alphabet these days) – and their stellar stock market performances of the past few years has continued in the first six months of 2018 despite a number of serious headwinds.

Technology companies in general have been buffeted by Donald Trump’s trade battles, in particular the idea of restricting Chinese investment in US companies and limit American technology exports to China. There have also been individual difficulties – sometimes of their own making – for the top companies to confront, but their share price has continued to march on.

Faang share prices Faang share prices

Facebook saw its shares slide in March when it was revealed it had suffered a massive data breach associated with data firm Cambridge Analytica, but its market value has still climbed 11% since January to value the business at $568bn (£431m).

Google shares have lagged behind the other five on worries about privacy issues and possible increased regulation, but parent company Alphabet still reported an 84% rise in quarterly profits in April. It is now worth $778bn, up 7% on the year.

Apple has faced concerns about slowing iPhone sales, especially for its top-of-the-range $1,000 iPhone X, although its latest results seemed to ease those fears. With the boost of an increased investment in the company in May by Warren Buffett, who normally shies away from tech companies, Apple shares have climbed nearly 10% so far this year to value it at $912bn. It is well on track to become the world’s first $1tn company.

Meanwhile, Amazon marches on in its own bid for world domination. Its last quarter showed profits had more than doubled to $1.6bn, helped by strong sales in its core business and by its purchase of Whole Foods Markets. It continues to move into new areas, including challenging Sky and BT for premier league football coverage. On Thursday it announced a new march into the pharmacy business with the purchase of Pillpack, a start-up online drugs distribution business – battering the share prices of huge established players such as CVS and Walgreens Boots Alliance. Despite a series of attacks by Trump, Amazon’s shares have jumped by 45% in the past six months, giving it a market value of $825bn.

Facebook Twitter Pinterest Netflix is now bigger than Disney thanks to shows such as Stranger Things. Photograph: Jackson Davis/AP

But out of all the Faangs, the standout success this year has been Netflix. Its market value has more than doubled to $172bn – making it bigger than Disney. The company has found success with the likes of Stranger Things and Queer Eye, and has signed up Barack and Michelle Obama for their own series. It is perhaps the only one of the five which can still be described as a disruptor, rather than a fully established business.

In total, the Faangs are now worth $3.25tn compared with the current valuation of Britain’s top 100 companies of £2.1tn. Their surge since January compares with a flat performance from the FTSE 100, a 2% fall on the Dow Jones Industrial Average and a 1.6% rise on the S&P 500.

These soaring valuations mean that the top slots in the Bloomberg Billionaires list is dominated by tech entrepreneurs, with Amazon’s Jeff Bezos leading the way with a net worth of $141bn.

Can the boom continue? Apart from the continuing uncertainties about Trump’s trade outbursts, there are concerns about tech companies’ current sky high valuations, which rekindle memories of the dotcom boom of the late 1990s, when loss-making businesses dominated the stock market before coming crashing down to earth. There is also the threat of increased regulation following the well-rehearsed privacy issues.

But there is a key difference to the dotcom era: these companies are profitable. In a recent note Goldman Sachs strategists Peter Oppenheimer and Guillaume Jaisson dismissed fears of another tech bubble, saying: “Unlike the technology mania of the 1990s, most of this success can be explained by strong fundamentals, revenues and earnings rather than speculation about the future.”

Trump’s tax reforms earlier this year also allow companies to repatriate cash from overseas, allowing them to pay out more in dividends to investors and providing another support for the shares. Apple, for example, plans to bring back almost $252bn which it currently holds overseas and recently announced a 16% increase in its quarterly dividend and a $100bn increase in its share buyback programme.

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Russ Mould, investment director at asset manager AJ Bell, said the five – with the possible exception of Netflix – are leaders in their fields and are making impressive profits at a time of modest economic growth, providing products and services people are willing to pay for.

He added: “These companies generally have little debt, lots of cash and are thus seen as ‘safer’ than many other firms – and these funds are being used to pay out huge dividends and buybacks to shareholders in the case of Apple.”

But he warned: “The danger for bulls is that these valuations leave little margin for error should something – anything – go wrong. While [they] are currently seen as almost safe haven stocks, owing to their perceived immunity from wider economic, trade or geopolitical concerns, this very perception and the valuations attributed to them could mean they are anything but safe.”