Mr. Epstein and Mr. Robertson, in their research, looked at 4,045 election-related searches on Google and Yahoo during a 25-day period from mid-October through Election Day. They found that the pro-Clinton articles swamped pro-Trump news.
“The algorithms are not programmed with an equal time rule,” said Mr. Epstein, a vocal Clinton supporter. “They are programmed to put one thing ahead of another in a way that is highly secret and ever-changing.”

He said his experiments show the power of news searches to affect politics and has found that he could boost support for a candidate by as much as 63 percent after just one Google search session. That is based on five experiments Mr. Epstein ran in two countries in which study participants changed their opinions of a candidate based on a manipulated search engine. He has dubbed this the “search engine manipulation effect.”
A separate study by Nicholas Diakopoulos, now at Northwestern University, analyzed the Google search results on Dec. 1, 2015. He searched for the names of all 16 presidential candidates and discovered Democrats, on average, had seven favorable search results among Google’s top 10. Republican candidates, meanwhile, had only 5.9 positive articles in the top 10.

Mrs. Clinton had five positive search results but only one negative on the first page, according to the study. Mr. Trump had four positive and three negative search results on the first page. Sen. Bernard Sanders, another Democratic candidate, had nine positive results without a single negative, and Republican candidate Sen. Ted Cruz had no positive results.

Mr. Diakopoulos ran a second study during the summer before the election and found the vast majority of sources selected for Google’s news box were left-leaning outlets. The New York Times, CNN and The Washington Post accounted for nearly 50 percent of Google news sources. Articles from Fox News, the only conservative news source among the 113 featured by Google during Mr. Diakopoulos’ study, appeared about 1 percent of the time.

Google eliminated the news box in November. Company spokeswoman Maggie Shiels said the box’s algorithm picked up news across the internet.
“There are several hundred signals that go into surfacing an answer,” she said. “The algorithm does not focus on political party or ideology.”

The company is secretive about the algorithm and insists it is constantly tinkering with the formula. But it says it promotes articles based on “freshness, location, relevance and diversity.”

“As a result, stories are sorted without regard to political viewpoint or ideology and you can choose from a wide variety of perspectives on any given story,” the company says on its online explainer.

Analysts have caught some deeper glimpses over the years, based on testing and on information gleaned from patent applications Google has filed, saying Google judges trustworthiness and importance of a news site, how much content it produces and even length of stories to gauge whether to elevate a site’s content.

News operations, just like other website owners, invest a lot of time and money trying to figure out Google’s system, and an entire industry known as search engine optimization, or SEO, claims to offer shortcuts to earn more eyeballs.


“If you are getting a certain perspective from the major news outlets, that is going to be passed on through social media, which is the last link in the chain,” he said.
But Mr. Epstein said the concern about who is creating the algorithm is just as concerning as the program itself.

“When accused of a liberal bias, these companies say, ‘It’s not us; it’s the algorithm,” he said. “That is so hilarious because they programmed the algorithm.”

Facebook workers raise questions
Accusations of an indirect bias may not carry as much weight if not accompanied by accusations of direct bias by the social media companies.

In May 2016, a group of several former Facebook workers told technology blog Gizmodo that they routinely suppressed news about prominent conservatives, including Mitt Romney, Rand Paul and the American Conservative Union’s Conservative Political Action Conference. The employees, who worked as ‘news curators,’ also said stories reported by conservative outlets such as Brietbart and Newsmax were dismissed unless The New York Times, BBC or CNN covered the same article.

Facebook denied the accusations and said an internal study found virtually identical rates of liberal and conservative new topics. The company did concede bias could have occurred through improper human actions and it would take steps to prevent it from happening in the future.