This is a totally made up stat.
It's supposed to mean "If I miss a single paycheck, I'm screwed. Not gonna make rent, car gonna get repossessed, have to decide which utility bill to pay and which to get shut off....."
When you see a stat in some news article saying "70% of Americans live paycheck to paycheck," it's guaranteed bullshit.
1. Typically, the source is basically a pull commissioned a shady debt consolidation firm or personal loan provider. Almost every article on this cites a "study" by LendingClub.Com.
2. Question wording matters, hugely. If you ask "would it hurt to miss your next paycheck?" or "do you feel like you don't have enough money left over at the end of the month?" you'll get a majority agreeing. If you specify something like the definition I provided above, the percentage drops precipitously. People that make six figures, but max out their 401K, put money into their kids college funds, have multiple car notes, take multiple vacations every year, will agree that they live paycheck to paycheck if you don't accurately define it.
3. Only 78% of people age 25-65 are even in the labor force. You're telling me an overwhelming majority of (>90%) of people in this country who receive a paycheck are "struggling financially"? The poverty rate in America is 11%. The numbers just don't make sense if you dig even an inch deep into them.