Revered New Jersey rockers Bruce Springsteen and Jon Bon Jovi sang together for Sandy victims at Madison Square Garden. Neil Young played a potentially jarring ballad about a girl - "Like a Hurricane" - before 2,000 screaming fans at the Borgata.

In recent weeks, high-profile fund-raising events have contributed to a charity drive that has raised an estimated $310 million since Sandy made landfall Oct. 29 near Atlantic City.

The announcement Tuesday night that the televised 12-12-12 concert raised $50 million brought cheers from fund-raisers.

But experts who track charitable giving say the flow of charity to the East Coast over the last six weeks has been hampered, principally by the timing of the storm but also by a variety of factors, from perceptions of Northeastern U.S. affluence to the surrounding media coverage.

With donations still coming in and audited charity numbers not set to be released until next year, the fund-raising picture remains unclear.

While comparing Sandy with other disasters is complicated by questions of scale, the tally thus far is a fraction of the $1 billion raised in first month after Hurricane Katrina struck New Orleans in 2005.

But it is more than seven times the total raised in the 19 months after a tornado devastated Joplin, Mo., according to the Giving USA Foundation, a Chicago nonprofit that works with Indiana University to track philanthropic giving.

"Charitable giving in 2012 was a lot different than it was in 2005," said Geoff Brown, executive director of the foundation. "We were in the middle [then] of several years of an economic upswing, and the timing was different. It was summer and not the fourth quarter."

Americans lead the world in charitable donations, about $300 billion a year.

Whether a tsunami strikes Japan or a hurricane the Atlantic seaboard, that number stays relatively flat, said Daniel Borochoff, president of the nonprofit CharityWatch, which serves as watchdog for the philanthropic sector.

That leaves charities to compete for a relatively fixed donation pool, and by the end of the year, many Americans already have committed whatever portion of their income they set aside for charity.

"Giving is pretty much 2 percent of GDP," Borochoff said. "A lot of it depends on the news coverage. With Sandy, we're seeing a lot of it is property damage rather than people's lives. I'm not surprised it hasn't been more."

The late-year timing was compounded by negotiations to try to avoid the fiscal cliff on Jan. 1, when a half-trillion dollars in tax hikes and spending cuts are scheduled to go into effect, something experts believe is affecting philanthropy.

The biggest fund-raiser for disaster relief is the American Red Cross, which as of Dec. 17 had raised $202 million to help Sandy victims get back on their feet, from handing out clothing and meals to offering health care.

Renee Cardwell Hughes, chief executive of the Red Cross's Southeast Pennsylvania division, said news reports immediately following the storm, about mansions falling into the ocean, left many potential donors with the false impression that only the wealthy were impacted.

"In the very beginning, you heard it," she said. "But as the media began to dig into the story and it came out this storm hit every sector of society, that changed pretty quickly."

The standard trajectory for disaster giving is that donations peak in the event's immediate aftermath and then trickle out over the months following.

Gulf Coast giving, however, tripled from its first-month total to almost $2.7 billion, according to Giving USA.

The question of the scale of Sandy's destruction relative to Katrina hangs over fund-raising efforts.

Sandy, which Gov. Christie has called "our Katrina," is likely to be the second-costliest storm in U.S. history.

But Katrina resulted in an estimated $108 billion in damages and left 1,800 people dead. Sandy is estimated to have caused around $80 billion in damage with a death toll of less than 150.

"We've been trying to caution people not to compare Sandy with Katrina. They were both large storms, but they were different in nature," said Melanie Pipkin, a spokeswoman for the Red Cross.

Fund-raisers from various groups were unanimously positive about the success of Sandy efforts compared with past disaster relief drives.

"It's really been amazing. The outpouring across the country has been remarkable. I can't say it's anything I expected," said Mary Pat Christie, wife of the governor and chair of the Hurricane Sandy New Jersey Relief Fund, which has raised $25 million.

But as aid flows to hard-hit communities such as Long Beach Island and Seaside Heights, grim reports from the Red Cross of families who had been living paycheck to paycheck having lost their homes are competing with the region's reputation as one of the most affluent parts of the country.

"With Katrina, the people who got hit were already so desperately poor," said Borochoff, of CharityWatch. "Around the country, there's a lot of 'if you could afford to live in New York or New Jersey, you don't need my money.' "

On Late Night With Jimmy Fallon last week, the musician Billy Joel, who grew up on Long Island, took on that perception, joking that the helipad at his seaside mansion had been damaged before turning serious and asking viewers to help less affluent victims.

"A lot of people think everybody in New York, Long Island, New Jersey, that we've got a lot of money," he said. "There's a lot of people that don't have a lot of money, a lot of middle-class, working-class, or poor people who really got hit."