You’re reading Significant Digits, a daily digest of the numbers tucked inside the news.

2 days

Baltimore Ravens offensive lineman and MIT mathematical doctoral student John Urschel announced yesterday his retirement from professional football after three years in the league. The decision comes two days after an ongoing study of brain tissue of former professional football players found an alarmingly high rate of chronic traumatic encephalopathy among donors. [ESPN]

3

Three Republicans — Senators Lisa Murkowski of Alaska, Susan Collins of Maine and John McCain of Arizona — joined 48 Democrats to vote against a third and seemingly final (for now) attempt to repeal portions of the Affordable Care Act, including the individual mandate. The 51-49 early morning vote, and Majority Leader Mitch McConnell’s subsequent remarks, mean that for now the Affordable Care Act appears unscathed despite complete GOP control of the federal government. [FiveThirtyEight]

2 million

The number of monthly active users of Twitter dropped by 2 million in the U.S. compared to the company’s previous earnings report, to 68 million. Still, daily active users — the junkies like me — were up 12 percent year-over-year. [CNN Money]

$506 million

A judge ruled that Apple infringed on patents held by the University of Wisconsin in its iPads and iPhones and owes the Wisconsin Alumni Research Foundation $4.35 per infringing unit. That adds up to about $506 million. [Ars Technica]

$86.5 billion

The really, really rich guys on earth have most of their wealth tied up in shares of the company or companies they own. That means that a particularly solid day for, say, Amazon can mean that Jeff Bezos can find himself the richest person in the world for a few hours — as happened Thursday. [Bloomberg]

$350 billion

Endowments held by private colleges, up 61 percent over the (post-recession) six-year period studied by the Chronicle of Philanthropy. [Chronicle of Philanthropy]

If you see a significant digit in the wild, send it to @WaltHickey.