Irving Kahn, who has died aged 109, was Wall Street's - and probably the world's - oldest active stockmarket investor.
Kahn began his career with the brokerage firm of Kuhn Loeb and made his first trade in June 1929, selling short 50 shares of a red-hot stock called Magna Copper which he believed was over-valued; his $300 stake, borrowed from an in-law, more than doubled when the Great Crash struck four months later. But he was not by nature a short-term speculator: rather, he said in an interview 85 years later: "I prefer to be slow and steady… If my arguments for the investment haven't changed, then I should like the stock even more when it goes down."
It was an approach he had learned in the 1930s from Benjamin Graham, the British-born Columbia Business School professor who was the father of "value investing" - the technique of picking, and holding for the long term, stocks that represent "a dollar selling for 50 cents" and thereby carry a built-in "margin of safety". Kahn attended Graham's evening classes at Columbia, worked with him as a research assistant and business associate.
Kahn went on to become a partner of Abraham & Co, which was acquired by Lehman Bros, and in 1978 he founded his own brokerage and investment advisory firm, Kahn Brothers, which grew to manage funds of $1bn. Much of his time as chairman was devoted to poring over technical journals and company reports in search of "value where others have missed it", having long since "stopped wasting time on what people claimed a stock was worth and started looking at the numbers". His preferred time horizon for this process was "decades": he advised other investors to tune out prevailing market views and ignore the modern world's "superfluity of information… all this static in the air".
He also cautioned against excessive borrowing, and supported proposals to reintroduce a separation of retail banks from those that trade in securities, because "I wouldn't lend you a dime if I knew you loved to gamble at a casino". Financial crises, he opined, were too often the result of "a bunch of gamblers going crazy on the floor of the exchange".
The remarkable longevity of Kahn and his siblings, without serious illness, became the subject of medical-school study: his sister Helen almost reached 110, his brother Peter died at 103 and another sister, Leonore, at 101. The diminutive Irving had smoked until he was 50 and preferred cheeseburgers to salad, but at 108 he still commuted the short journey from his apartment to his office three days a week to discuss investment possibilities with his son Tom, who had taken over the running of the firm, and his analyst grandson Andrew; the latter had been reading to him from The Economist on the day he died.
The son of a Polish immigrant salesman of electrical goods, Irving Kahn was born in Manhattan on December 19, 1905 and was educated at DeWitt Clinton High School in the Bronx before dropping out of college to find work as a Wall Street clerk.
He was a founder member of the New York Society of Security Analysts and a co-founder of the New York City Job and Career Centre, which offered vocational training to high-school pupils. His standard advice to young people starting out was: "Figure out what you like to do and do that. Don't worry about the money. If you're good at what you do, the money will take care of itself."
Irving Kahn, who died on February 24, married, in 1931, Ruth Perl, whom he met at Columbia University when she was studying for a doctorate in psychology; she died in 1996. They had three sons, of whom two survive him.