How big is an ideal candidate pipeline?

For recruiters, our pipeline is everything. This is how our work is measured. How soon can we fill our pipelines, how diverse are they, and will our pipeline of candidates be adequate to fill the role in an acceptable amount of time. But how do we know exactly how many candidates should be in our pipeline?

Several years ago, I learned a new way to approach my candidate pipelines which I’ve taken with me and taught to recruiters and hiring managers since. It’s a concept called the Optimal Stopping Problem, which is a statistics theory used to describe the best time to take a particular action or make a decision when faced with a number of options. More on the theory in a moment. 

The reason this idea was important to me is because there has always been a natural tension between hiring managers and recruiters about the health of a candidate pipeline. Once in a room of Engineering Leaders, my friend and former hiring manager, Chris Martin, asked me if the insurgents had blown up my pipeline because it was seemingly nonexistent. Ha ha ha.

In another meeting with one of my Engineering leaders, he expressed concern that for some of his roles there were only one or two candidates, while for other roles there were quite a few comparison candidates. Why wasn’t my team being more consistent with the pipelines across each of his roles? I told him that some roles are so unique that we may not have the opportunity to see a large number of candidates within our timeline. Also, given a candidate's need to make quick decisions, when we find what appears to be a unicorn candidate we may need to move faster and hire them quickly.

He asked me if I’d heard of the Optimal Stopping Problem. This theory helps you make a difficult choice at the right time. To understand this more clearly, think of big decisions you might make like choosing a spouse, a new house, or in our case picking a candidate. What the Optimal Stopping Problem tells us is you have only a certain number of candidates you can evaluate before the first and second candidates will drop off (see image below). What he was trying to show me at the moment was that his team wouldn’t really know they were making a good decision if they didn’t have enough comparison candidates.

However, as I sat with the concept more, I realized the Optimal Stopping Problem could be used for both the Recruiter and the Hiring Manager sides of the recruiting process. From a recruiter’s perspective, we do extensive intake meetings learning all of the requirements and nice to have qualifications for a role. We sort through hundreds or thousands of applications and spend time sourcing profiles, to build a diverse slate of candidates. Often our hiring managers want us to continue to build up the pipeline, seemingly to no end, in order to ensure success.

Using the Optimal Stopping Problem, we see that at some point we’ll need to stop and focus on a final pool of four to six ideal candidates, because as we move forward with more and more interviews, eventually we will start to lose our first finalists, who will have dropped off and gotten other roles, or worse, have gotten frustrated with the time our interview process is taking. 

Additionally, the more candidates we interview, the more chance the team will suffer from analysis paralysis. An abundance of options can lead them to fear making a choice, to forget who they’ve interviewed along the way, or worry that the criteria isn’t correct. For example, each candidate can present a new set of nice to have qualities, so the longer you drag things on, the more nice to haves you may decide you need. The process never ends.

From a candidate’s perspective this must seem so overwhelming. Given that most roles these days receive 200 applicants in the first hour, and now we’re adding to this the idea that ideally we only fully evaluate four to six finalists, how does a candidate stand out? We don’t want candidates to be discouraged. It’s possible to jump late into the pipeline by being a super stand out candidate who messages the hiring manager, the recruiter, or even the CEO. 

In the end, we will always look to our candidate pipelines as the true measure of our worth as recruiters. I will work to ensure I have an Optimal Stopping Problem number of qualified candidates to make the right decision, while also encouraging my hiring managers to make decisions quickly so we don’t lose someone amazing.

What’s your method for ensuring your pipelines are solid? Have you come across the Optimal Stopping Problem? I’d love to hear about it. Leave me a comment. I find it all so interesting.

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That’s So Interesting is a passion project series of articles on the recruiting, candidate and hiring experience. I’m also available for consulting assignments large and small, including executive search, contingency engagements, and TA or HR leadership strategy.