Top Five Insurer Market Cap vs. S&P 500

notes
Surprisingly, the market cap of the top five/six insurers has kept pace with the S&P since 2015.
Author

Stephen J. Mildenhall

Published

2026-02-16

Modified

2026-02-16

Collective market narratives—like the recent AI-driven “tech-only” boom—can warp our perception of other sectors. I saw a LinkedIn post recently1 that made me do a double take: the claim was that the market capitalization of the top U.S. insurers has basically kept pace with the S&P 500 since 2015. My gut reaction was skepticism. Given the last decade, and especially the AI-driven run-up in mega-cap tech, I expected insurers to lose ground as a share of the index, not quietly hold their own.

I asked GPT and Gemini to pull year-end market caps for the S&P 500 and a simple insurer basket (BRK, TRV, PGR, HIG, ALL, and Chubb, treating ACE as the predecessor). The punchline: the numbers they pulled mostly agree, and the insurer-to-S&P ratio looks surprisingly steady over 2015-2025. It is a nice reminder that a quick, sanity-check style analysis like this has become easy to do with LLMs, and also that the result can still surprise you.

Being able to spin up a comparative analysis in a Quarto document with a few prompts makes the barrier to “fact-checking the feed” almost non-existent.

Here is the data each model uncovered, together with a comparison model-to-model and insurers-to-market.

Table 1: Gemini’s estimates.
Year ALL BRK CB HIG PGR S&P TRV Ratio
2015 24.05 324.44 31.89 14.91 13.80 18,230 28.46 2.4%
2016 27.29 401.94 52.23 15.48 15.74 19,340 29.27 2.8%
2017 37.57 488.67 59.59 17.15 25.46 22,820 31.77 2.9%
2018 28.46 502.52 53.35 13.86 27.90 21,030 27.80 3.1%
2019 36.43 553.65 64.48 19.41 34.94 26,750 31.62 2.8%
2020 33.43 542.56 64.61 15.93 49.47 31,660 32.32 2.3%
2021 33.73 669.11 80.73 22.55 54.79 40,350 38.49 2.2%
2022 35.96 680.80 89.47 23.57 69.48 32,130 43.94 2.9%
2023 36.63 776.39 91.17 24.19 93.10 40,040 43.51 2.7%
2024 51.05 978.31 111.39 32.12 140.30 52,200 54.69 2.6%
2025 54.47 1,083.80 122.80 32.68 133.60 61,100 64.71 2.4%
Table 2: GPT’s estimates.
Year ALL BRK CB HIG PGR S&P TRV Ratio
2015 24.00 325.00 37.92 17.00 19.00 17,900 33.00 2.5%
2016 27.00 402.00 61.48 18.00 21.00 19,270 35.00 2.9%
2017 38.00 489.00 67.83 20.00 33.00 22,820 37.00 3.0%
2018 27.00 502.00 59.31 16.00 35.00 21,030 32.00 3.2%
2019 36.00 552.00 70.35 22.00 42.00 26,760 35.00 2.8%
2020 33.00 544.00 69.47 18.00 58.00 31,660 36.00 2.4%
2021 33.00 669.00 83.26 23.00 60.00 40,360 38.00 2.2%
2022 36.00 682.00 91.56 24.00 76.00 32,130 44.00 3.0%
2023 37.00 777.00 92.20 24.00 93.00 40,040 43.00 2.7%
2024 51.00 984.00 111.93 32.00 141.00 52,871 55.00 2.6%
2025 55.00 1,074.00 124.97 39.00 133.00 61,747 66.00 2.4%
Table 3: Comparison, Gemini to GPT.
Year ALL BRK CB HIG PGR S&P TRV Ratio
2015 0.2% -0.2% -15.9% -12.3% -27.4% 1.8% -13.8% -5.8%
2016 1.1% -0.0% -15.0% -14.0% -25.0% 0.4% -16.4% -4.3%
2017 -1.1% -0.1% -12.1% -14.3% -22.8% 0.0% -14.1% -3.6%
2018 5.4% 0.1% -10.0% -13.4% -20.3% 0.0% -13.1% -2.6%
2019 1.2% 0.3% -8.3% -11.8% -16.8% -0.0% -9.7% -2.2%
2020 1.3% -0.3% -7.0% -11.5% -14.7% 0.0% -10.2% -2.7%
2021 2.2% 0.0% -3.0% -2.0% -8.7% -0.0% 1.3% -0.7%
2022 -0.1% -0.2% -2.3% -1.8% -8.6% 0.0% -0.1% -1.1%
2023 -1.0% -0.1% -1.1% 0.8% 0.1% 0.0% 1.2% -0.1%
2024 0.1% -0.6% -0.5% 0.4% -0.5% -1.3% -0.6% 0.8%
2025 -1.0% 0.9% -1.7% -16.2% 0.5% -1.0% -2.0% 1.1%
Figure 1: Comparison of Gemini and GPT estimates and overall market cap trend.
Figure 2: Top six (ALL, BH, CB, HIG, PGR, TRV) and five (excluding BRK) vs. S&P 500, market cap trend.

Footnotes

  1. Trying to find this link was surprisingly hard, it should be called UnLinkedIn.↩︎