5 trillion-dollar companies — including Nvidia, Apple, and Amazon — have been behind most of the S&P 500's 10% gains this year

• The S&P 500 index is on a tear, rising nearly 10% this year.
• But most of the gains are from a quintet of stocks that have surged massively this year.

The S&P 500 index is on a tear, rising nearly 10% so far this year — in stark contrast to a 13% decline over the same period last year.

But gains in the benchmark index — which tracks a broad range of sectors such as banks, manufacturing, tech, and retail — are thanks to massive upswings from just five companies: Apple, Microsoft, Alphabet, Amazon, and Nvidia, all of which have posted outsized gains in market cap this year so far.

The companies are part of the elusive club of firms touching $1 trillion in market valuation, with Nvidia becoming the latest company to briefly hit the milestone before giving up some gains.

Collectively, the five companies have raised their market cap by about $2.9 trillion in 2023 — contributing 96% of the almost $3 trillion gains in the S&P 500's market value this year, Fortune reported on Wednesday.

This means the rest of the 495 companies in the S&P 500 contributed to just 4%, or $110 billion in the index's gain, per Fortune.

The outsized gains of the five companies have also put the benchmark index under scrutiny for concentration risk, as Insider's Zahra Tayeb reported on Sunday.

"Today's US price action is another reminder that this year's favorable equity market performance is still about a handful of tech stocks. Not only is the Nasdaq outperforming again but, also, the S&P 500 would be in negative territory were it not for #Nvidia," Mohamed El-Erian, a top economist and Allianz advisor said in a tweet last Thursday when the S&P500 settled nearly 1% higher.

The S&P 500 Index closed flat at 4,205.52 on Tuesday.

Read further to know the five bigwigs' market capitalization — or marcap — gains this year, in descending order:

1. Apple: $718 billion in marcap gains

The world's largest company by market cap, Apple shares ended 2022 at $129.93 apiece. They are now 36% higher at $177.30 apiece.

This takes Apple's market value to $2.8 trillion as of Tuesday from $2.07 trillion at the end of 2022.

Apple has so far avoided mass layoffs, unlike its high-profile Big Tech peers. The company even managed to post solid fiscal second-quarter earnings that beat market expectations, with strong iPhone sales supporting revenues.

CEO Tim Cook told CNBC on May 4 that Apple doesn't plan to conduct mass layoffs. However, the tech giant is cutting costs and has slowed hiring, Cook added to the network.

"I view that as a last resort and, so, mass layoffs is not something that we're talking about at this moment," Cook told CNBC's Steve Kovach.

2. Microsoft: $672 billion in marcap gains

Microsoft shares ended 2022 at $239.82 apiece and are now 38% higher at $331.21 piece, taking the company's market cap to nearly $2.5 trillion now.

The tech giant's shares were boosted by posting fiscal third-quarter earnings that beat Wall Street estimates. In particular, AI boosted sales at its cloud computing businesses over the period, the company disclosed.

Microsoft has an ongoing partnership with OpenAI and in February launched a new version of its search engine Bing that's powered by an AI tool it says is "more powerful than ChatGPT."

However, Microsoft wasn't immune to the tech slowdown that hit the tech industry in 2022. In January, it announced 10,000 job cuts by the end of the third quarter as customers cut back on spending amid economic uncertainty.

3. Nvidia: $628 billion in marcap gains

Nvidia — the stock market darling of the moment — closed out 2022 with its share at $146.14 apiece. They are now at $401.11 — representing stunning gains of nearly 175% this year so far.

On Tuesday, the chipmaker's market cap briefly hit the coveted $1 trillion mark for the first time. But the market capitalization is just shy of $1 trillion now.

Nvidia's recent rally came thanks to the rise in the California-based chipmaker's share price following the company's blockbuster first-quarter results from the generative artificial intelligence boom.

Particularly, shares of the company rose 25% last Thursday.

The gains in Nvidia's shares have boosted the fortune of cofounder and CEO Jensen Huang by 160% this year so far, according to the Bloomberg Billionaires Index. Huang is now worth $36 billion, making him the 34th richest person in the world.

4. Alphabet: $426 billion in marcap gains

Google parent Alphabet's share price closed out 2022 at $88.23 apiece and is now 40% higher at $123.67 apiece, taking its market cap to $1.58 trillion.

Alphabet reported better-than-expected first-quarter results in April, with its cloud unit turning in a profit for the first time, per Bloomberg.

This was after the tech giant managed to turn in solid earnings after slashing 6% of its workforce in January.

CEO Sundar Pichai said in a memo to employees announcing the job cuts that he took "full responsibility for the decisions that led us here."

"Over the past two years we've seen periods of dramatic growth," Pichai wrote in the email. "To match and fuel that growth, we hired for a different economic reality than the one we face today."

5. Amazon: $391 billion in marcap gains

The e-commerce giant closed out 2022 at $84 apiece, but its share price is now trading at 45% higher at about $122 apiece.

This takes Amazon's market cap to $1.25 trillion — up from $857 billion at the end of 2022.

Amazon's share surge comes on the back of first-quarter profit that beat Wall Street estates, with operating income coming in at $4.8 billion as compared to the $3 billion analysts polled by Bloomberg were expecting.

The tech giant's gain also came with a lot of pain for its employees. Just this year alone, Amazon conducted two rounds of layoffs impacting 27,000 roles collectively. This was after cutting 10,000 employees in 2022.

CEO Andy Jassy attributed the "uncertain economy" and rapid hiring in a January memo announcing its largest round of job cuts ever.