Big Tech's share of the S&P 500 reached record level in August

The gap between the weighting of the five largest companies in the S&P 500 and the 300 smallest rose to the highest ever at the end of August, according to data from the Leuthold Group.

Why it matters: The concentration of wealth in a few massive U.S. tech companies has reached a scale significantly greater than it was before the dot-com bubble burst.

• In August, five companies — Apple, Microsoft, Amazon, Facebook and Alphabet — held a share of the S&P 500 that was 9% greater by market cap than the index's 300 smallest companies. This was a record amount.

What they're saying: "These trillion-dollar tech juggernauts have boosted their market-cap weight in 11 of the past 12 months — zooming from 15.8% of the S&P 500 last September, to 23.9% in August," Phil Segner, a Leuthold Group research analyst, said in a recent note to clients.

• "What’s even more remarkable is that this trend has persisted during a 33% downdraft and a 60% updraft. September’s relative wobble in the 'Top 5' has trimmed its weight back to 21.7%, which is the largest month-to-month decline since 2000."
• "Even with the trim, the current weight of the S&P 500’s Top 5 is still well above the Tech Bubble’s high of 18.1%."