Sharon Winick, 49, and her husband Michael consider themselves middle class. They have three children and own a home in Chevy Chase, Maryland, where Michael is a network administrator. Sharon is a paralegal turned stay-at-home mom. Between his work, her occasional side jobs and their investments, they bring in roughly $125,000 a year. Yet they struggle to make ends meet. "The amount of money we spend every month is more that we make, it's been that way since we had our first daughter," Winick said. With the children all now approaching college age, tuition is a big concern. "I don't know how we are going to do it without borrowing from the house."

The amount of money we spend every month is more than we make. Sharon Winick married, mother of three

About 70 percent of the U.S. adult population consider themselves middle class, both in income and mindset, according to recent findings in Northwestern Mutual's 2017 Planning and Progress study. That's roughly the same as five years ago, Northwestern Mutual said. However, the actual number of middle-income households in the United States has been shrinking for decades, and made up only half of the population in 2015, down from 61 percent in 1971 according to the Pew Research Center. Over that period, both the share of upper-income households and lower-income households grew. Still, slightly more than half of those who considered themselves middle class had household incomes ranging from $50,000 to $125,000 a year, according to Northwestern Mutual, in line with Pew's parameters — adults whose annual income is two-thirds to double the national median, about $42,000 to $126,000 annually for a household of three. The rest of those who said they are middle class — but aren't — fall either above or below that benchmark, Northwestern Mutual said.