Online misinformation about election fraud plunged 73 percent after several social media sites suspended President Trump and key allies last week, research firm Zignal Labs has found, underscoring the power of tech companies to limit the falsehoods poisoning public debate when they act aggressively.

The new research by the San Francisco-based analytics firm reported that conversations about election fraud dropped from 2.5 million mentions to 688,000 mentions across several social media sites in the week after Trump was banned from Twitter.

Election disinformation had for months been a major subject of online misinformation, beginning even before the Nov. 3 election and pushed heavily by Trump and his allies.

Zignal found it dropped swiftly and steeply on Twitter and other platforms in the days after the Twitter ban took hold on Jan. 8.