Gary Shapiro has one interview question he always poses to job candidates: How soon can you start?

It's a straightforward inquiry, but a person's response can be immediately disqualifying, says Shapiro, the longtime CEO of the Consumer Technology Association, a trade organization that produces the annual CES trade show in Las Vegas.

If an interviewee says they can start in less than two weeks — and they're currently employed — "they don't get the job, because they'll treat us the way they treat that former employer," Shapiro, 68, tells CNBC Make It. The pass-fail question doesn't apply to candidates who are currently without a job, he notes.

"I want an [employee] with a level of commitment to their organization — even if they don't love their job — where they won't leave their employer hanging," says Shapiro, who's been the CTA's CEO for the past 33 years.

How people leave their jobs is "really important," he adds. The principle applies to his own employees who leave for other organizations: Departing under good conditions — for example, by giving at least two weeks' notice — is often a consideration whenever the CTA rehires "boomerang" employees, Shapiro says.

Shapiro asked his go-to question while interviewing a candidate whom he ultimately hired as the CTA's chief operating officer, he says. Her response, as Shapiro recalls, was that she'd need up to six weeks to adequately transition from her former job.

"I was very thankful she answered" that way, he says. "I said, 'That's perfect. You got the job.'"

What the interview question is really asking

The question — and its make-or-break nature — may sound extreme "at face value," says Joyce Guan West, a San Francisco-based executive and career coach. You shouldn't deploy it as a standalone query, she adds — but if you ask it alongside other character-focused questions, you'll stand a good chance of effectively determining whether a candidate's values align with your own.

"I would be surprised if the majority of high-quality candidates, or candidates at a more senior level, would say less than two weeks," West says, noting that executive-level candidates often need more than two weeks to offboard from their current roles. "It seems like kind of a softball question that most smart people are going to answer correctly."

West recommends pairing Shapiro's question alongside others that probe why the candidate is interested in the role and the company, and why they're looking for a new role at all. A well-suited candidate will have done their research and offer enthusiastic, compelling answers — while steering clear of speaking negatively about their previous employment experiences, she says.

The additional questioning helps you find someone "who's going to do the right thing, as opposed to someone who's just looking out for themselves," West says.

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