Back in the conference room in San Francisco in May, Zachary Oleksiuk, another analyst, gave his report to the group via video conference from Princeton, N.J.. He was in charge of keeping track of Occidental Petroleum, an oil and gas exploration company based in Los Angeles, some of whose directors had served for many years and were richly rewarded. BlackRock, with a $4.6 billion stake in Occidental, is its largest shareholder.

“As you all know, Occidental has been a perennial company of concern to us,” Mr. Oleksiuk said. Just a few weeks before, he met with two key Occidental directors to voice BlackRock’s dissatisfaction. “I sent our message to them in person,” he told the group. The message was that BlackRock planned to vote against the company’s longest-serving directors and its entire compensation committee. BlackRock was certainly not the only investor objecting to the board, and a week after Mr. Oleksiuk’s meeting with Occidental, the oil company issued a statement clarifying its succession planning, hoping to quell some of the concern. It wasn’t enough.

This month, Ray Irani, the chairman and former C.E.O., stepped down from his post after failing to receive the support of a majority of investors. Whether it was BlackRock’s “engagement” or the vote, or both, one thing was clear: shareholders made a difference.