Over the past 50 years, the world has undergone profound changes. The internet, which didn’t exist in 1975, is now an integral part of nearly every aspect of our lives. Additionally, globalisation has opened up new markets and economic opportunities.

The investing landscape has transformed in tandem. In 1975, stock markets were dominated by the oil and automative industries. The technology sector was in its infancy, and few could have predicted the seismic shift that would lead to the rise of tech giants now dominating the market.

This article will explore these changes and highlight the importance of holding a diversified portfolio in an unpredictable market.

The top 10 stocks: a comparative table

The table below shows the biggest publicly listed companies (or ‘stocks’) in the US in 1975 and today. We’ve chosen to focus on the US because it allows us to provide a like-for-like comparison, as comprehensive data on global stocks from 1975 is not available. Also, the US has long been the world’s largest and most influential economy, with its companies often leading the global market. Overall, the data illustrates the significant changes that have occurred over the past 50 years.

Sources: 1975 data from Fortune magazine’s annual list of the 500 largest companies in the US, ranked by total revenue and published on CNN Money. 2025 data from the S&P 500 Index (which tracks the 500 largest US companies), ranked by weight, as at 13 May 2025. *Alphabet appears twice on the S&P 500 because it has two classes of publicly traded shares – one class comes with voting rights and the other does not.

1975: dominated by oil

In 1975, the top 10 stocks were dominated by oil companies, including Exxon Mobil, Texaco and Gulf Oil. The global economy was even more reliant on oil in 1975 than it is today, with oil powering industries, transport and energy production. Renewable energy was virtually non-existent at the time, and the world's energy needs were primarily met by fossil fuels. The importance of oil was underscored by the energy crises of the 1970s, which led to sharp increases in oil prices. This surge in prices made oil companies extremely profitable and attractive to investors.

The automotive sector was also prominent, with General Motors and Ford Motor securing spots on the list. This was largely due to the post-World War II economic boom, which spurred a significant increase in consumer demand for automobiles. 

However, there were early signs of the technology industry’s emergence. ITT Industries, a conglomerate, was a major player in the telecommunications industry, though its business activities also extended to defence, hospitality and financial services. IBM, which was ninth on the list, was a more notable presence in the tech sector in 1975. That year, IBM launched its first ‘portable personal computer’, with a price tag as high as $20,000 (more than $116,000 in today’s money) and weighing 25kg¹. 

2025: the rise of technology

By 2025, the top 10 has seen a dramatic shift. Technology companies now dominate the list, with Apple, Microsoft, Nvidia, Amazon, Meta (Facebook) and Alphabet (Google) all making the cut. Tesla, while primarily known for its cars, is also considered a tech company due to the advanced technology it integrates into its products. These seven tech giants are often referred to as the ‘Magnificent 7’ because of their market dominance, strong financial performance and influence on consumer behaviour and economic trends. 

Berkshire Hathaway, a conglomerate with more than 60 subsidiaries including insurer Geico, battery-maker Duracell and restaurant chain Dairy Queen, also makes the list. However, its largest investment is in tech giant Apple, further cementing the tech sector’s influence. 

Broadcom, though less well-known, is another major player in the technology industry. The company produces semiconductors, which are essential components in modern electronics, ranging from smartphones to data centres. 

The importance of diversification

The transformation of the top 10 stocks over the past 50 years underscores a critical lesson for investors: you can’t predict the future or pick the winners with certainty. In 1975, oil companies were the giants of the market, but by 2025 technology firms have taken the lead. 

This shift highlights the unpredictable nature of market dynamics and the importance of investing in companies across a wide range of industries and regions of the world. A globally diversified index fund will do this for you. It will invest in emerging companies when they are small and continue to hold them as they grow into future leaders.

As Vanguard’s founder, Jack Bogle, once said: “Don’t look for the needle in the haystack. Just buy the haystack.”

Different companies will inevitably fall in and out of favour, but by owning a diversified portfolio, you can potentially reap the benefits from those that are performing well while mitigating losses from those that aren’t. This balanced approach is key to long-term investment success.

Investing with Vanguard

At Vanguard, you can invest in shares by buying funds. These funds contain hundreds, if not thousands, of individual shares, making it a low-cost and easy way to diversify your investments.

You can do this yourself by choosing from our wide range of low-cost individual funds. Or you can keep things simple by picking one of our LifeStrategy funds or Target Retirement funds, which combine different types of investments in one ready-made portfolio.

For clients in our managed services, we select investments for you based on your attitude to risk, so you don’t need to worry about picking funds. We also manage your portfolio for you, making changes only when necessary to maintain the right level of risk.

¹ Source: oldcomputers.net

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