No one knows exactly how much money Michael R. Bloomberg has given to Johns Hopkins over the years.
He has acknowledged up to $107.5 million. The real total might be several times that amount. Sources have tied this week's anonymous $100 million gift to the munificence of the mayor of New York. Another anonymous $100 million that established an institute to study malaria in 2001 is widely believed to have come from Bloomberg.
The same is true of a few million that came with an order to quickly do a cosmetic renovation of the Homewood campus in 2000. Bloomberg might well have given even more, as there are several other substantial anonymous donations that have appeared in the Hopkins coffers since this member of the Class of 1964 began opening up his wallet for his alma mater.
"He genuinely likes what Hopkins does," said Alfred Sommer, who was dean of the public health school when it was named for Bloomberg in 2001. "At the Bloomberg school, he is our biggest cheerleader and booster."
To put these figures into perspective: The Hopkins institutions were founded when Baltimore businessman Johns Hopkins left the unprecedented amount of $7 million on his death in 1873, split equally between the hospital and the university.
According to inflation calculators, that $7 million would be worth about $108 million today - a fraction of what Bloomberg is thought to have given.
The university is still called Johns Hopkins, but besides the school of public health, the Bloomberg name is on a physics building financed with an $8 million gift, and a $1 million gift endowed a professor of humanities named after Bloomberg's mother, Charlotte.
He has been especially generous to public health, a place that often has difficulty raising funds because, as Sommer often says, by definition it doesn't have grateful patients, only people who never get sick.
"He in essence came up with our slogan - 'Saving lives, millions at a time,'" Sommer says of Bloomberg. "He goes around telling people, 'This institution saves more lives than any institution in the world.'"
Bloomberg, 64, did not respond to a request for an interview for this article. In previous interviews, he has acknowledged that he was an indifferent student, though an enthusiastic fraternity member, while at Hopkins. He said he studied hard the first semester of his senior year, getting good enough grades to parlay his engineering degree into an admission to the Harvard business school.
"Hopkins taught me how to think," Bloomberg said in 1999. "It certainly didn't teach me how to be an electrical engineer. Even God couldn't have done that."
A meteoric rise on Wall Street was cut short when the company he worked for - Salomon Brothers - was sold in 1981 and he was asked to leave. Bloomberg took his severance settlement, estimated at around $20 million, and started the company that would make him a huge fortune.
In his last years at Salomon Brothers, Bloomberg's brash personality got him farmed out to the technology division, not considered a prime assignment.
He took what he learned there and started a company that delivered financial information to investment firms, using computers to give up-to-the-minute figures, particularly on bond sales that until then required laborious calculations involving huge ledgers.
The business took off and then expanded into a financial news empire. It is privately held. Published estimates put Bloomberg's worth at $4 billion to $5 billion.
In the past, Bloomberg has urged donors not to be anonymous, contending that if people saw that someone prominent was giving money, they would be inclined to give, too.
But it is a little delicate for Bloomberg to put his name on a $100 million gift to a Baltimore institution, because since 2002 he has been mayor of New York. He was overwhelmingly re-elected for a second term last year. He left the Hopkins board of trustees, which he chaired from 1996 to 2002, a few months after he became mayor.
"He's very generous to New York now," Sommer points out. "He gives money to a wide variety of charitable institutions there, cultural, educational, social service.
"He is just someone who is an extraordinarily generous guy," Sommer says. "And he does feel very warmly toward Hopkins. There is no question about that."
Though Hopkins officials say the first donation received from Bloomberg was in the year he graduated - for $5 - it was far from evident that he was going to develop those warm feelings.
He had paid little attention to Hopkins before Morris W. Offit, a fellow alumnus also at Salomon Brothers, recruited him for the board of trustees in 1987. Bloomberg has credited his board experience with giving him an appreciation for Hopkins.
"It was really when I became a trustee that I started to realize the breadth of Hopkins, that what I thought of the school as an undergraduate is only one part of what they do," Bloomberg said in 2001.
He has likened his philanthropy to an investment - he likes to see returns on the money.
"I think he likes the way Hopkins is run - that people make good use of the money and are in a position to make a real difference in the world," Sommer says. "He really and genuinely wants to make a positive difference in the world."
When Bloomberg added $45 million to a previous gift of $55 million in 1998, that $100 million was tied for the ninth-largest in history to private education. But the stakes have since been raised - that gift is now tied for 33rd.
Bloomberg is known to be competitive and might not be satisfied with 33rd. But there is time - he has said he will go into philanthropy full time when he leaves office in four years.
"I can't think of anything else you can do with your money that can give you as much satisfaction," he said in 1998. "You can buy a yacht or you can help cure cancer. As far as which one is going to put a smile on my face as I'm falling asleep at night, I think the answer is clear."