A new study issued by the San Francisco-based Newtithing Group indicates that private donations to charities could be tripled if wealthy individuals and middle-income Americans who have investments worth more than $100,000 were sparked to be more philanthropic, the New York Times reports.

The proprietary Newtithing study found an additional $242 billion could be donated to charity without harming donors' fiscal health, up from current total giving levels estimated at $110 billion, the Times reports.

"Our main point is that generosity has been based too much on income," Newtithing Group founder Claude Rosenberg told the Times. "With capital for many people being so much larger than [their] income, there is enormous untapped capacity to give."

An estimated $190 billion - or more than three-quarters of the additional $242 billion - could come from individuals in the top three tax brackets, according to Newtithing Group's estimates.

The group's research - based on 1996 Internal Revenue Service tax data - shows that the more than 14 million filers who earn adjusted gross incomes of $50,000 to $74,999 while owning average investment assets of approximately $118,000 "could on average increase their annual giving by 21 percent, from $1,322 to $1,600 per filer - and under normal circumstances still see their wealth rise," Rosenberg said.

Rosenberg is the retired chairman of RCM Capital Management.

His 1994 book, "Wealthy and Wise: How You and America Can Get the Most Out of Your Giving," details Newtithing's original research on increased philanthropic opportunities.

Newtithing Group is a California corporation that donates any annual surpluses to charity and whose findings are distributed either free or at cost to nonprofit organizations, individuals and interested parties.