People have plenty of conspiracy theories about the libertarian Competitive Enterprise Institute — viewing it as an extension of the Koch brothers’ empire or a subsidiary of Exxon Mobil.

The truth turns out be a bit more complicated, as revealed by the companies and interest groups that sponsor its annual fundraising dinner, which took place Thursday night at the J.W. Marriott in Washington.

According to a copy of the dinner program provided by the group, the biggest single donor to the group is Google, which gave $50,000, while Facebook kicked in $25,000.

Other donations were more predictable, including $110,000 from the energy sector and the same amount from conservative foundations — three of which are associated with billionaires Charles and David Koch.

Lawson Bader, CEI’s new president, said the dinner list shows that the group has “a pretty diverse group of supporters.” The fact that fossil-fuel firms and rail companies that transport coal and oil rank as highly makes sense, Bader said, because CEI has “been working on energy and environmental issues longer than other” Washington groups.

At the same time, he said, CEI sees itself as a strong defender of privacy and civil liberties, which attracts support from tech firms.

“We are very committed to the idea of free enterprise and individual liberty,” he said. “CEI does see itself as more libertarian than conservative.”

The dinner’s scheduled keynote speaker was Sen. Rand Paul (R-Ky.), whose political stock is particularly high at the moment. “I have no doubt that having Rand Paul as the keynote speaker probably helped drive some of the increased interest in the dinner,” Bader said. “It’s hard to test that theory.”

The group ranks its donors according to the value of five metals — chromium, tungsten, nickel, copper and tin. The designations come from a bet between economist Julian Simon and ecologist Paul Ehrlich, who predicted that the metals would be more scarce in 2005 than in 1980, the year of the wager. (Ehrlich lost the bet.)

Bader convinced his mother, Jeannie, and his brother, Cole, to buy dinner tickets at $250 each.

When asked whether he thought his mother should have made a bigger donation, Bader replied, “No comment.”

(Washington Post Co. chairman and chief executive Donald E. Graham is a member of Facebook’s board of directors.)