Richard Russell, who shared his technical analysis with subscribers through the influential Dow Theory Letters since 1958, has died. He was 91.

He died Nov. 21 at his home in La Jolla, California, his family said in a message to subscribers on the publication’s website. He had entered a hospital a week earlier and was diagnosed with blood clots in his leg and lungs “and other untreatable ailments,” his family said. He returned home under hospice care.

An adherent of the investing principles of Charles Dow, founder of the Wall Street Journal, Russell published his newsletter continuously from 1958, never missing an issue in more than half a century.

In his last column, published Nov. 16, Russell wrote: “I read 10 newspapers a day, but the news is getting increasingly difficult to digest down to something understandable, and the vast array of news sources becomes more and more complex. I can only imagine what the newspapers will look like in 10 years.”

Stock analyst Robert Prechter wrote in his 1997 book: “Russell has made many exceptional market calls. He recommended gold stocks in 1960, called the top of the great bull market in stocks in 1966 and announced the end of the great bear market in December 1974.”

In 1969 Russell devised the Primary Trend Index, composed of eight market indicators that he never publicly divulged -- his own secret recipe. When his index outperformed an 89-day moving average, it was time to buy. When it underperformed the 89-day moving average, a bear market was at hand.

“The PTI is a lot smarter than I am,” Russell said. The benchmark is unrelated to the Russell 2000 and other indexes maintained by Seattle-based Russell Investments.

Bearish Call

Russell said forecasting the stock market became more difficult as the number of investors swelled and trading became instantaneous. In 1990, at the start of a 10-year bull market, he wrote in Barron’s that stocks were entering a bear market that would undo the gains of the prior 15 years.

The title Dow Theory Letters reflected Russell’s lifelong interest in the market observations of Dow, who created the Wall Street Journal in 1889 and penned his principles in a series of editorials from 1899 to 1902. One Dow principle holds that a stock-market rally relies upon transportation and industrial equities both surpassing recent peaks.