I have a rude habit that I can’t shake whenever I’m at a restaurant with someone who is picking up the check or splitting the bill with me.

I always, always sneak back to the table and check to see what they tipped.

Yes, it is totally a moral litmus test on several levels. The size of a gratuity is insight into character or life experience. Or math skills.

And it’s the big issue on the D.C. ballot Tuesday, one that some say threatens the American culture of tipping and, ultimately, our restaurant industry.

The practice of tipping goes back to 18th-century English pub culture, when a coin would be given “To Insure Promptness” — T.I.P. — according to Michael Lynn, a professor at the Cornell University School of Hotel Administration, in his paper “The Psychology of Restaurant Tipping.”

It’s not illegal to stiff a waiter on a tip, if you want to join America’s current, vigorous discussion about what is ethical and what is law. And unless you’re eating out with me, probably no one but the server will know if you skimped.

But it says a lot about who we are.

When I look to see how much my dining companion tipped, it’s not like I’m searching for a life partner (he passed that test 25 years ago) or vetting new hires for my corporation. I do this partly out of curiosity, but mostly, I do this because I don’t want the waitstaff to get shafted. I know how it feels.

About 30 percent of the time when I peek — 100 percent in the case of one family member — I throw in a little extra cash on top, because the tip was a disgrace.

When I was growing up, generous tips put a roof over our heads and clothes on our backs. Disgraceful tips tightened our belts. My parents both worked as servers throughout my childhood, and then I waited tables in high school and college.

Tips are what makes the District’s $3.33-an-hour tipped wage — $2.13 on the federal level — doable.

But this whole arrangement is in question in the nation’s capital right now, as D.C. voters decide on Initiative 77, which would abolish that puny wage employers are allowed to pay when an employee is tipped and would eventually set a standard, $15-an-hour minimum wage for all workers.

The minimum-wage debate is complicated. It always has been. And in this case — when livelihoods are often dependent on the whims of a customer — it is especially messy.

Workers at some of the city’s hottest bars and restaurants routinely make twice the proposed minimum wage. They stand to lose a lot. But to the people at the diners — the people who get tips in change, if that — $15 an hour sounds like a veritable windfall.

Then there are the restaurant owners. Many say the initiative will force them to raise prices, possibly lay off workers.

But here’s what I know: Tipping, for many of us, is firmly a part of American culture. We’re the ones who can’t stop tipping, even when we travel to a country where tipping isn’t standard.

Could this law be part of a larger, state-by-state cultural shift, like bike helmets, same-sex marriage or the driving age? Will it ultimately sweep the nation and kill America’s restaurant boom as places are crushed by the cost of a true minimum wage?

Probably not.

If a restaurant is already in trouble, chances are the “Out of Business” sign will go up quicker if this law is passed, according to a recent Harvard University study on tipped-wage legislation. Minimum-wage laws have had little impact on healthy businesses.

But let’s face it, much of America’s restaurant mania is about entertainment, not sustenance. It’s doubtful that the folks who are hugely ridiculed for eating $19 avocado toast, but continue eating it, will be scared away when their guac on bread goes up to $20.

It’s at the restaurants that are more about sustenance — like the diners and coffee shops my mom worked at most of her life — where tips shine a light on the most vulnerable of this 2.6 million-person workforce.

A busy day at a coffee shop means a hustle in $1 and $2 increments. It’s hardly the makings of a three-figure tips day. So for those folks, relying on the good graces of tippers is a dodgy way to make a living.

Remember, my lifelong snooping tells me that about 30 percent of people will get away without tipping fairly — or at all — if they can.

The Washington business community and the D.C. Council are largely against the measure, siding with the current culture of tipping as enough.

Maybe, but I always come back to what columnist and author Dave Barry calls the Waiter Rule, which has nothing to do with tipping. It says, “A person who is nice to you, but rude to the waiter, is not a nice person.” It’s a rule often invoked by business folks as a hiring test.

For instance, a candidate interviewing for a general counsel position lost the job when she was “amazingly rude” to someone cleaning tables during the interview, Panera Bread founder and chief executive Ron Shaich told USA Today.

It’s also a good guideline when choosing a potential bae. If they’re rude to the restaurant waitstaff, drop them.

But perhaps we are a city of optimists, where everyone passes the Waiter Rule — and tips generously. I sure hope so, because we’re about to find out.

Twitter: @petulad

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