The number of millionaire households in the United States continues to escalate, but the divide between wealthy and middle class is also growing, according to Phoenix Marketing International’s latest “Wealth & Affluent Monitor” report.

The number of millionaire households has grown by 1.3 million since before the recession to 6.8 million households last year, with nearly 250,000 added between 2015 and 2016, Phoenix said. This represents a 4 percent one-year increase in the number of millionaire households.

The biggest gains in millionaire households were recorded in Utah, Michigan, Arizona and Ohio, while the most declines were seen in New Mexico, South Dakota, Vermont and Maine.

“The concentration of wealth in the U.S. continues to deepen as the top 1 percent of wealthiest U.S. households now holds 24 percent of liquid wealth. Non-affluent households, representing 70 percent of households, control less than 10 percent of the nation’s liquid wealth,” Phoenix said. The greatest asset growth was among households with between $1 million and $10 million in investable assets, which grew by $809 billion to a total of $17.8 trillion between 2015 and 2016.

By comparison, near-affluent households in the U.S. with between $100,000 and $250,000 saw investable assets decline by $79 billion during the same period, to $2.6 trillion, suggesting a need for financial advice in this wealth segment, the report said.

“Our research reveals stark geographic, demographic and economic differences within the broad wealth and affluent market,” said David Thompson, managing director of affluent practice at Phoenix Marketing International. “The trends we’ve seen over the past 10 years show a deeper and wider wealth divide as families in the near- and emerging affluent segments fall further behind financially.”