North Dakota’s oil production is booming — and it’s minting millionaires.

Over the last year, North Dakota climbed more than any other state in terms of share of households that are millionaires, skyrocketing 14 spots: The state is now ranked 29th in the country, according to Phoenix Marketing International’s rankings. One spot ahead of Florida and behind Wisconsin, North Dakota was the only state to see its share of millionaires increase by more than 0.5 percentage points.

“It’s a little rare to see a state jump like North Dakota did,” said the firm’s managing director. According to the rankings, 4.59 percent of the state’s households are worth more than $1 million.

Analysts credit the jump to the state’s oil boom and the corresponding increase in land values in the state, particularly for farmers who are selling their land. But as one local chamber-of-commerce president told the Wall Street Journal, North Dakotans aren’t the types to show off their newfound wealth.

“The only way you know a Bakken [oil patch] millionaire is he’ll be driving a new truck and might have taken his wife on vacation,” he said.