As the old adage goes, the one constant in life is change. It's true of companies as well. Although it seems like today's titans will forever remain on top, the same seemed true of yesteryear's powerhouses. It wasn't.

With that as the backdrop, how have things changed for publicly traded companies over the course of the past 40 years? A lot.

Today's biggest companies

Today's biggest companies (as measured by market capitalization) should come as no surprise. From a massive market value of $4.2 trillion all the way down to a still-massive market cap of $2.4 trillion, here are the market's five biggest names right now, from biggest to smallest.

  1. Nvidia (NVDA -2.78%)
  2. Microsoft (MSFT -2.68%)
  3. Apple (AAPL -0.16%)
  4. Alphabet (GOOGL 1.13%) (GOOG 1.04%)
  5. Amazon (AMZN -1.46%)

My how things have changed over the course of the past 40 years.

Man sitting at a desk doing some paperwork in front of a laptop.

Image source: Getty Images.

1985's biggest companies

There isn't absolute agreement on which companies qualify as 1985's biggest. Energy outfit ExxonMobil as we know it today didn't exist until Exxon merged with Mobil in 1999, for instance, while General Electric has since been carved up into several different industrial entities. It also seems like AT&T is missing from this list, but remember, the 1980s were an era of significant breakups and acquisitions in the telecom industry, including the breakup of Bell the year before. The AT&T of today isn't the same AT&T it was then.

Regardless, based on data provided by Goldman Sachs and the American Enterprise Institute, Visual Capitalist says these were the five biggest companies back in 1985, from biggest to smallest:

  1. International Business Machines (IBM 0.51%)
  2. ExxonMobil (XOM -2.82%)
  3. General Electric (GE -0.96%)
  4. Philip Morris International (PM 0.28%)
  5. General Motors (GM 0.42%)

For perspective, IBM's market cap at that time was around $30 billion -- small by today's standards, but enormous for the day.

The takeaway

The takeaway for investors, of course, is to never assume any giant organization's size means it's built to thrive indefinitely. Newer businesses are always on the horizon.