The Internal Revenue Service has painted a statistical portrait of just how sweet big estates were – and how quickly health savings account contributions were growing — back in 2007, as the investment markets were peaking.

The IRS has included data on estate tax returns, individual tax deductions, and other topics in the latest Statistics of Income Bulletin.

A review of estate tax returns filed from 2001 to 2007 shows that the number of estates filing any estate tax return fell to 38,031 in 2007, from 108,071 in 2001, because of changes that freed more Americans from the estate tax.

But the number of estate tax returns filed for “wealthy decedents” – those with at least $3.5 million in gross estate, increased to 14,281 in 2007, from 9,440 in 2001.

The total asset portfolios of those wealthy decedents increased to $146 billion in 2007, or an average of about $10 million per estate, from $91 billion in 2001, or about $9.6 million per estate.

The percentage of stock in those portfolios fell to 38% in 2007, from 47% in 2001, and the percentage in cash increased to 7.8%, from 7.2%.

The percentage in investment real estate increased to more than 15%, from 9.4%.

Meanwhile, a Statistics of Income Bulletin report comparing information from 2006 and 2007 individual tax returns shows that the number of taxpayers who deducted HSA contributions increased rapidly, to 593,000 in 2007, up 65% from 359,000 in 2006.

The amount contributed to HSAs increased 73%, to $1.5 billion.

In 2007, HSA contributions amounted to about 12% of payments made to individual retirement accounts.

Total adjusted gross income increased to $8.9 trillion in 2007, up 8.2% from $8 trillion in 2006.

Other individual income tax statistics:

- In 2007, 18,394 individual taxpayers reported $10 million or more in adjusted gross income.

- HSAs were especially popular among taxpayers reporting $100,000 to $200,000 in AGI, with 143,181 taxpayers in that income category deducting HSA contributions.