We’re in line at a Publix supermarket in west Florida. Waiting. There aren’t enough people to work the checkout registers. The checkers are stressed.

My friend grimaces. Clad in shorts, sandals, and slightly disheveled, he looks like an absentminded professor — or a long-term resident of Margaritaville.

We’re about to sail off to beautiful Useppa Island on Florida’s Southwest Gulf Coast, but I can feel his mood darken. I ask what’s wrong, expecting him to say he wants to be on the water and this is a waste of time. But he doesn’t.

"These people are our support system. Without them, we can’t live the way we do. I couldn’t do mathematics. You couldn’t write. If they’re not making it, we’re going to have a problem," he says.

A friend since childhood, he’s a world-class mathematician. He took his first course at Columbia when he was 12. Went to MIT and Harvard at the same time. Got his doctorate at Princeton, then hung out at the Institute for Advanced Study, former home to Einstein and Oppenheimer. Now a professor at a prestigious university, his income puts him in the top 5 percent of all earners.

And he doesn’t own a tie.

My friend isn’t quite like Spock in Star Trek, but sentiment doesn’t play a big role in his life. That’s why his comment gets my attention. He’s not doing the grandstanding that some do, decrying CEOs whose pay averages 400 times that of the average worker. He’s simply aware that a lot of people are making $8 to $12 a hour, with minimal benefits, so others can buy Dom Perignon at Sam’s Club for $107 a bottle instead of $220.

Call it the Miracle of Supply Chain Management. To my relentlessly logical friend, the standard of living gap is looking like an unsustainable spread.

Is it? We’ll never know by looking at CEO salaries. To know if the social contract is working and whether the body politic is healthy, we need to compare much bigger groups. IRS tax returns, for instance, tell us that the top earners are pulling ahead of workers at the bottom of the income pyramid.

To be in the top 5 percent of all income tax returns in 1986, you needed to have at least $62,377 in income. By 2001, the last year for which figures are available, you’d need at least $127,904 to be in this group. That’s an income growth rate of 4.9 percent a year. While earning that income, the top 5 percent paid a stunning 53.25 percent of all income taxes.

During the same period, the bottom 50 percent saw their income rise from no more than $17,302 to $28,528. That’s an annual increase of 3.4 percent, barely ahead of the 3.0 percent inflation rate for the period. They paid 3.97 percent of all income taxes at the end of the period.

More important, the top 5 percent earners went from having 3.6 times as much as the bottom 50 percent to 4.5 times as much. That’s way less than the 400x multiple we hear so much about.

But it’s still a big change, leaving us with two big questions: Can the multiple go much higher without creating a de facto have/have-not society? And can anything be done about it?

Scott Burns (www.scottburns.com) has been a personal finance writer since 1977 and has been syndicated in newspapers across the United States since the late 1980s. Send your questions and comments about managing your wealth via e-mail to privateclubs@clubcorp.com.