
Warren Buffet and his offsider the late Charlie Munger are dead set Slack Investor Heroes – and a reminder that the USA offers a crucible for outstanding qualities to emerge in individuals – as well as, in some presidential types, some not so good qualities. Mr Buffet is a great investor and philanthropist and full of insightful but humble advice that is worth heeding. Every November he writes a letter to his Berkshire Hathaway shareholders and it is a delight to read in full. This will be his last shareholder letter as he is retiring at the grand age of 95.
‘Our stock price will move capriciously, occasionally falling 50% or so as has happened three times in 60 years under present management. Don’t despair; America will come back and so will Berkshire shares.’ – Berkshire Hathaway 2025 Newsletter
Even investors as great as Warren Buffet are not immune to large market swings. After all, it is your long-term performance that is the most critical for a lifetime investor.
‘Since 1965, shares of Warren Buffett’s conglomerate, Berkshire Hathaway (BRK.B), have delivered a compounded annual return of 19.9% — almost double that of the S&P 500 over the same period.’ – Investopedia using data from the Berkshire Hathaway 2024 Newsletter
Warren Buffet liked to look at current market valuation (S&P 500) as a ratio with the current US Gross Domestic Product (GDP). At 30 June 2025 the ratio was 217%. A long way above the trend line and a warning that the S&P 500 was growing at a rate much faster than the general economy – this is a danger sign.

Market Value – November 2025 Update
Slack Investor also likes to keep up to date with how the markets are travelling for value and he has been using charts for the Cyclically Adjusted Price to Earnings ratios (CAPE). This value is also known as the Shiller P/E Ratio after Robert Shiller the economics professor that made this measure popular. Slack Investor first started using CAPE as a ‘value’ tool in September 2021. The most recent post on Market Value was mid-April 2025 about 6 months ago.
For the following charts, Slack Investor uses monthly CAPE data from Barclays, the 40-yr mean is calculated and plotted together with the latest actual CAPE values up until 31 October 2025. A ‘fair value’ zone is created in green where the CAPE is within one standard deviation of the mean (average) – click images for better resolution.
ASX 200 CAPE Value 22.89 (11% above long-term av.)

FTSE 100 CAPE Value 18.24 (5% above long-term av.)

S&P 500 CAPE Value 39.76 (59% above long-term av.)

The UK and Australian markets are not too overvalued. However, in terms of the Shiller P/E the S&P 500 has entered some lofty territory. Unfortunately, whenever the S&P 500 has a large correction the effects are usually felt in other markets.
There is some good research that links CAPE to long-term returns … and future returns are what gets Slack Investor excited. The predictive skill of the Schiller CAPE is not very good over 1-yr and 5-yr periods. However, it does show some skill for periods of 10 years and longer. The tight spread around the trend line indicates that the Shiller P/E might have some predictive skill.

If this relationship holds, the average S&P 500 10-year annualised forward returns are predicted to be close to zero or negative. This indicates that now is not a good time to start buying the S&P 500. Tech stocks (with high P/E) have fallen sharply lately and this could be early signs of a readjustment.
Slack Investor is not one with predictive skills. He just plods along – staying mostly invested and knowing that he has his stable income pile to ride out any market gyrations. Cripes … even the great Warren Buffet’s Berkshire Hathaway stock had 11 negative years between 1965 to 2024. Slack Investor could only dream of emulating the Buff’s long term compounded annual return of 19.9% over 55 years.


















