Is BRK performance close to S&P 500 at 2:1 leverage using interest-free float?

[LearningMachine]

https://www.berkshirehathaway.com/letters/2019ltr.pdf shows annualized return of 20.3% for BRK market value and 10.0% for S&P 500 from 1965 to 2019.

 

Similarly, https://www.berkshirehathaway.com/letters/2018ltr.pdf shows annualized return of 18.7% for BRK book value and 9.7% for S&P 500 from 1965 to 2018.

 

During those years, Berkshire Hathaway had the opportunity to invest more and more float from insurance companies, and others have said BRK effectively got a leverage of 2:1 while paying no interest on that float. 

 

Could that leverage explain a big part of the performance difference between BRK and S&P 500?

 

If BRK had access to the same float and at some point, had switched to investing in S&P 500 returning 10% instead of picking stocks & operating companies, could it have achieved about the same results?

 

Would love to hear insightful thoughts to help me understand deeper.

[Thrifty3000]

Awesome question. Pretty sure BRK would have had to pay taxes on the S&P 500 dividends, which would have reduced relative outperformance pretty significantly over the long rung.

 

Whereas with an operating business like GEICO BRK could just throw the advertising spend into hyperdrive and gobble up market share (even a caveman could do it).