(CNN) Sen. Bernie Sanders on Monday released a decade of tax returns, providing new insight into how the Democratic socialist senator from Vermont became a millionaire between his two presidential runs.

According to returns provided by his campaign, Sanders and wife Jane's bottom line jumped from $240,622 in 2015, the year he launched his first White House bid, to $1,073,333 a year later, as the once obscure lawmaker became a political sensation on the left and a bestselling author with royalties pouring in.

Since that first run, Sanders and his wife made a total of more than $2.79 million, putting them in the category of the super-rich.

Sanders in a statement said the returns "show that our family has been very fortunate."

"I consider paying more in taxes as my income rose to be both an obligation and an investment in our country," he added. "I will continue to fight to make our tax system more progressive so that our country has the resources to guarantee the American Dream to all people."

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