A new study by the IRS shows that much of the money charities earn from business activities comes from selling products, services, and advertising.

Charities in 2004 — the latest date for which statistics are available — reported that 74 percent of their $5.5-billion in total business income not related to their charitable missions stemmed from their profits on those three types of pursuits.

Nearly 17 percent of the total “unrelated-business income” reported by charities stemmed from capital gain net income, partnership and S corporation income, and debt-financed income, the report said.

The IRS said that while these categories of investment income “comprised a relatively small proportion” of charities’ total unrelated-business income, “the total amount of these items rose 73 percent between 2003 and 2004.”

The IRS published the data — which are derived from Form 990-T tax returns filed by tax-exempt organizations — in its newly released Statistics of Income Bulletin for Winter 2008. Those tax forms used to be kept confidential but a new law passed by Congress makes them public.

Meanwhile, the IRS recently released statistics that show that deductions claimed for charitable contributions rose to $183.4-billion in 2005, compared with $165.6-billion in 2004, an increase of nearly 10.8 percent.

From 2003 to 2004 deductions claimed for charitable contributions increased by 13.6 percent.

The statistics show that the average contribution claimed on donors’ tax returns rose from $4,076 in 2004 to $4,432 in 2005, the highest average donation recorded in the quarter-century for which the government has data.