The divergence between the broader stock market and a handful of massive technology companies continues to hit new milestones. BTIG technical strategist Jonathan Krinsky said in a note to clients Sunday that the market-cap-weighted S & P 500 is abnormally far ahead of the equal-weighted version of the index as measured by their respective relative strength index, or RSI, a momentum indicator. The regular S & P 500 closed with an RSI above 70 last week, while the equal-weighted version finished with an RSI below 50 on the same day. “That’s the first time in history (data back to 1990) that has happened. The closest we got to those readings was July ’98 and July ’21. The former marked the peak before a -20% decline while the latter saw a marginal new high, a modest 3.6% decline, then resumption of the uptrend,” Krinsky’s note said. The RSI is a way to compare the average upward moves with the average downward moves of a stock or an index. The RSI is measured on a scale of 0 to 100. Readings above 70 are considered a sign of a stock or index being overbought. Excitement around artificial intelligence has led to several tech stocks becoming dominant weights in the S & P 500. In particular, Microsoft , Apple and Nvidia are all over $3 trillion in market cap. In the equal-weighted S & P 500, each company has the same influence on the index. The median market cap in the index is closer to the $33 billion value of Extra Space Storage . The performance gap between the market-cap and equal-weighted indexes is also large. Over the last 12 months, the SPDR S & P 500 Trust (SPY) is up 23.5%, while the Invesco S & P 500 Equal Weight ETF (RSP) is higher by just 10%. RSP 1Y mountain Equal weighted measures of the S & P 500, like the RSP, are underperforming the index itself. This disparity in size and performance has led to concerns about weak market breadth and whether that means that the bull market is on borrowed time. “Bulls continue to look for breadth expansion and a catchup to the leaders. While that’s always possible, we find it rarely works that way when the divergences get this deep and long-lasting,” Krinsky said.