BRK.B ... apparently it doesn't have the strong negative correlation needed to attract the algorithmic trading world. I only imply that, I haven't seen the data.

My Indian friend sent me the raw data for Nasdaq and BRK.B since 2021. Rough analysis, yearly brackets only:

2026
A) Nasdaq up 86x (53%): BRK up 41% / BRK down 59%
B) Nasdaq down 75x (47%): BRK down 48% / BRK up: 52%

2025
A) Nasdaq up 144x (58%): BRK up 57% / BRK down 43%
B) Nasdaq down 105x (42%): BRK down 51% / BRK up: 49%

2024
A) Nasdaq up 146x (58%): BRK up 58% / BRK down 42%
B) Nasdaq down 105x (42%): BRK down 47% / BRK up: 53%

2023
A) Nasdaq up 141x (57%): BRK up 66% / BRK down 34%
B) Nasdaq down 108x (43%): BRK down 62% / BRK up: 38%

2022
A) Nasdaq up 111x (45%): BRK up 80% / BRK down 20%
B) Nasdaq down 138x (55%): BRK down 75% / BRK up: 25%

2021
A) Nasdaq up 140x (56%): BRK up 59% / BRK down 41%
B) Nasdaq down 111x (44%): BRK down 52% / BRK up: 48%

2026 as example for how to interpret the numbers:
A1) The Nasdaq was up 86x = in 53% of all trading days in 2026
A2) In 41% of those "Nasdaq-UP-Days" BRK was up too, in 59% it moved down instead
B1) The Nasdaq was down 75x = in 47% of all trading days
B2) In 48% of those "Nasdaq-DOWN-Days" BRK was down too, in 52% it moved up instead

In other words:
In 2026 when the Nasdaq moved UP, in more than half the cases BRK moved down instead ("Why holding boring BRK when I can buy SpaceX instead?").
When the Nasdaq moved DOWN, in half the cases BRK moved UP instead ("I am scared; maybe a little less SpaceX and boring BRK instead").

I have no comparison with other equally boring stocks (JNJ etc.), but this seems to be highly significant, that 2026 BRK in half or even more than half the cases moved in the opposite direction of the Nasdaq.

Very different from 2023 when "only" in 1/3 of the cases BRK moved in the opposite direction (still a lot).

And definitely extreme when you compare 2026 with 2022: Then in 4/5 of all Nasdaq-UP cases BRK did the same, and in 3/4 of Nasdaq-DOWN cases too -> 2022 BRK moved far more in line with the Nasdaq than nowadays.

Strong quantitative support for my subjective observation since 1.5 years that BRK extraordinarily often (apparently half the time or even more) moves in the opposite direction of "the market" (in this case the Nasdaq, but it was similar for the S&P (I just asked my Indian friend for the S&P data with the same date range :)).