William O’Neil, an investment broker who started an equity research firm and brokerage before later creating Investor’s Business Daily in 1984, has died at the age of 90.

David Saito-Chung from IBD writes, “This combination of a successful printing firm and a unique quantitatively-driven database on stocks led to the first publication of Investor’s Daily, as it was then called, on April 9, 1984. Investor’s Business Daily later became a weekly print newspaper in 2016 as the company focused even more effort on developing its digital properties, notably Investors.com and MarketSmith, as well as premium online products such as Leaderboard and SwingTrader.

“In learning from great fund managers in the past, O’Neil also changed the game of investing by providing data on the quantity and quality of institutional ownership in the best stocks.

“This perspective, reported throughout his Datagraphs product and later through unique IBD ratings including the Accumulation/Distribution Rating, is known as the I in CAN SLIM, which stands for institutional ownership.”

Read more here.