Figures released to The Associated Press show a record 634 people reported incomes of more than $1 million on their 2011 individual tax returns, up from 532 in 2010 and 384 in 2009. In 2006, while North Dakota's oil boom was in its infancy, there were 339 so-called "income millionaires."
About 90 percent of the drilling in western North Dakota occurs on private land.
Tax Department analyst Kathy Strombeck said the increase in the number of North Dakotans with million-dollar incomes comes largely from royalties paid to mineral owners by oil companies.
"Oil has a lot to do with it," she said. "I imagine we'll see growth for a while as we ratchet up projection."
Through September, North Dakota already has set an oil production record for the fifth consecutive year and the state is on pace to best the previous mark by more than 50 million barrels. The state Department of Mineral Resources said crude production through September totaled more than 173.9 million barrels, up from the record 152.9 million barrels set last year.
Tax Department records show the average adjusted gross income in the state increased from $53,036 in 2010 to $60,947 last year. The average adjusted gross income on 2006 returns was about $43,300.
The number of returns has jumped from 339,000 in 2006 to 403,625 last year. The total reported income has increased from $14.6 billion to $21.9 billion during those years, data show.
Tax Commissioner Cory Fong said the higher incomes and the increase in the number of people filing tax returns in the state "adds to the narrative of what we've got going on here in North Dakota."
The oil industry has helped grow wages throughout the state and created hundreds of high-paying jobs. It also has an effect on other industries, including wholesale trade and manufacturing, he said.
"In a way, it's lifting all boats," Fong said.
A strong overall economy and healthy agriculture sector also are factors, Fong said.