Private foundations have seen their asset levels grow substantially since the recession, although the growth has not been consistent for all sizes of foundations, says a new study released Friday by Foundation Source, an organization that provides support services for foundations.

Overall asset levels have increased by 48 percent since 2008, according to the study, Trends in Private Foundation Investment.

Between 2008, the height of the recession, and the end of 2013, the assets for the 238 foundations included in the survey grew from $700 million to more than $1 billion, an increase of $334 million.

Despite nearly uniform investment portfolio performance for foundations of every size, the endowment balances did not grow at the same levels, Foundation Source says. Foundations with endowments of $1 million or more saw steady growth in the endowments, while those with less than $1million remained flat.

“This was likely because smaller foundations typically distribute a greater percentage of their assets than their larger counterparts,” says the survey.

Like many individual investors, the foundations increased their holdings in equities as the stock market recovered. In 2013, the foundations allocated 55.5 percent of their assets to equities, compared to 42.4 percent in 2008. Over the same period, cash holdings shrank from 20.5 percent to 12.8 percent.

According to Robert Chartener, Foundation Source CEO, “Private foundations have philanthropic commitments that depend on reliable investment returns. At no time has the pressure on their financial advisors to meet this challenge been greater than during this economically turbulent span of time. Our new report shows how our clients, together with their financial advisors, capitalized on improving markets these last few years.”

Although most foundations were happy with their advisor relationships, Foundation Source found areas where advisors could improve.

Advisors should help foundations create and update investment policies, Foundation Source says. Sixty-five percent of the foundations said they did not have a written investment policy and, of those that had a policy, 37 percent said they had not updated it in the last year.

Although 60 percent of the foundations said it was either somewhat important or critically important for advisors to work with the upcoming generations of foundation leaders, only half of the advisors had interacted with the next generation.