Silicon Valley Technology Center in San Jose, California/photo by Joseph Sohm/Shutterstock

The Standard & Poor's 100 index and the Silicon Valley 150, a list compiled by Fenwick & West, have some overlapping companies but many diverging corporate governance trends, a new survey finds.

David Bell, the Fenwick partner who authored the firm's 2018 Corporate Governance Practices and Trends report, said the continuation of dual-class voting structure trends in the SV 150 stood out to him.

The survey found 13 percent of SV 150 companies had dual class structures, an increase from last year, compared with 9 percent of S&P 100 companies.

“Any recent trend in IPOs isn't going to show up in the S&P 100 for some time. That's part of the difference,” Bell said. “Part of it is … by the time a company has gotten to the scale that it's in the S&P 100, not always, but often, the founders may not be as active with the company anymore.”

Both the S&P 100 and the SV 150 trended toward decreasing power concentrated in a combined chairman and chief executive officer role, though companies on both lists approached the issue in different ways.

SV 150 companies were less likely to appoint a combined chairman/CEO. In the 2018 proxy season, Fenwick's survey found only 32 percent of SV 150 companies had a combined role, compared with 63 percent of the S&P 100. But 83 percent of S&P 100 companies had lead directors, who can help balance the power of a combined chairman/CEO.

“In both the S&P 100 and the SV 150 it's a clear trend toward making sure—whether there's a separate seat, an independent chair, or it's a lead director—but having some way that you demonstrate that you have an independent voice that has a leadership role in the boardroom,” Bell said.

Companies in the SV 150 skew toward having fewer meetings than their S&P 100 counterparts. The median number of meetings for both groups is seven, according to the report, though many SV 150 companies said they meet less often.

SV 150 companies also, on average, had proportionately more insider directors, such as a CEO or founder, on the board. Bell said that's in part because the average SV 150 company's board is smaller than the average S&P 100 company's, so the same number of insiders is proportionally higher.

But bigger boards could be in the SV 150's future. A recently passed California law requires all companies in the state to have at least one woman on their boards by 2019. Companies with five board members must have at least two women, or three out of seven, by 2021.

In some cases, companies that don't meet the requirements and opt to add a woman without removing any men could get bumped to a larger board tier. They would then need to add even more women onto the board to comply. Bell said the new rule will especially impact smaller companies.

“There may be some companies that are below the SV 150 that are in California that have only four [all-male board members]. Unless they're going to take a male board member off to put on a woman, you're going to end up with larger boards,” Bell said. “And they may end up with considerably larger boards than they had planned.”

Fenwick's survey found 27 SV 150 companies had no women on their boards. While the majority of companies had at least one woman, most SV 150 boards have six or more directors, according to the report, requiring them to have at least three women directors. Only 26 companies met this criteria.