Last summer Bank of England economist Andy Haldane stated that long term interest rates were the lowest in five thousand years.

businessinsider.com - Chart years of interest rates history

I would argue that with rates that low Berkshire should have borrowed more money. (I should have, too. My neighbor refinanced his house with a 15-year, fixed rate mortgage at 2.0% interest with no points.) Over the past couple of years Berkshire has issued long dated, yen denominated notes at about 2% interest, but I would argue that Berkshire should have issued much more. Berkshire had a secure investment for the borrowed money, namely repurchase of Berkshire stock, which could be expected to return 8%-10% over the next 30 years, without leverage. If Berkshire made 8% on the equity it invested plus 8%-2%=6% on the borrowed money, then at a 1:1 ratio of equity to borrowed money (a conservative ratio with payments so low), Berkshire would make 14% on the equity used. Warren is rightly conservative about borrowing money, but the situation last summer was unique, on a thousand year time scale. He should have borrowed more. jmho.