Nalbantian cited an example from a company in the banking industry dealing with high turnover rates. When employees were asked during exit interviews, they noted heavy workloads and pay as key drivers of their decision to quit. But after correcting for these factors, the company's turnover rates didn't improve. A look at actual data suggested that career development and management stability were bigger factors in turnover, and focusing more on these areas led to improved retention rates.

“Every one of us has a whole set of potential employment alternatives,” Nalbantian said. “If you ask me once I've already made a decision to leave, chances are I've found something like better pay. But why was I even open to alternatives? Why was I looking, why was I responsive? It's not that people are deceiving you. We might not be asking the right questions, and they might not even be thinking of the answers.“

How does it work?

Their modeling involves gathering all available data–employee records on pay, performance, promotions, resignations, as well as data about the organization itself–and creating a statistical model that allows different variables to be isolated. From there, potential differences can be identified and used to create models determining probability of a specific outcome given a set of conditions.

“We have about 2 million records across a range of industries,” said Tauseef Rahman, principal of Workforce Strategy and Analytics, listing industries such as health care, insurance, media, transportation and hospitality. “This allows us to segment the data in a few ways.”

Specifically, they drilled down into the behaviors of millennial employees. The findings confirmed what most of us already know: millennials are job-hoppers. But that's no reason to give up hope. “There's a lot of variation in what drives this turnover that suggests there are things organizations can do to reliably effect turnover, potentially quite dramatically,” Rahman said.

Here are a few key misconceptions about millennials they found that could be affecting employee retention:

Myth: Base pay is less important than bonuses and incentives

One myth they tested was the belief that millennials are driven more by performance pay than other generations. But in fact, base pay matters more to millennials than other demographics.

That's because millennials today are faced with massive student debt, rent or a mortgage and a list of other fixed bills–and they need a fixed income to pay for it all. “There are enormous financial and career pressures on millennials,” Nalbantian stressed. “If pay becomes a lottery, don't be surprised if turnover goes up and engagement goes down. We need to understand our workforce and what's right for them.”

Myth: Promotions and career development drive millennials

Again, the data contradicts the common belief that the way to keep millennials is promote them and give them opportunities to develop their careers. In reality, all you're doing is helping them become more marketable.

“All else being equal, a millennial who has recently promoted is substantially more likely to leave the organization in the following year,” Nalbantian said.

They key phrase, of course, is “all else being equal.” There are a lot of other factors impacting any employees' career decisions. “We don't read this and say, 'keep all your millennials in place,'” Nalbantian warned. “You need to think strategically about this.”

As an aside, Nalbantian also pointed out that, in running data analyses for other generations, they found that lateral company moves are actually one way to increase retention among the Baby Boomer generation. “You want to keep them on and engaged, moving them laterally seems to be a pathway to achieving that outcome. We don't often think of mobility as a preserver of the older.”

Myth: Millennials need constant feedback about performance

There's a lot of talk about abandoning the annual performance review and focusing more on offering regular feedback and updates, a strategy purported to be better suited to the Millennial workstyle. And maybe it is–millennials don't really care about performance ratings, the data says.

In some models, higher performance ratings actually correlated to higher likelihood of turnover, another indication that millennials are looking for ways to increase their marketability.

Fact: Supervisors play a major role in millennial satisfaction

In running their analysis, the team also looked at the effect of the supervisor on each outcome. In the case of a promotion or job transfer, the influence of the supervisor can overcome the other factors. “Millennials are more sensitive to who they work with and report to than any other generation,” Nalbantian said. “Because the supervisor and group characteristics are so important, ensuring that you are considering not just whether someone's promoted, but the quality of that promotion, who they are with during the workplace may be essential to get the full value of those job changes.”

“We see, for example, that millennials are more likely to quit if their supervisor quits,” Rahman added. In addition, they're less likely to quit if their supervisor is a woman or has a high performance rating. In addition, if a supervisor quits, their millennial employees are likely to follow. “None of these relationships appear among other generations.”

Understanding the power of supervisor/employee relationships can have a huge effect on diversity and inclusion programs, Nalbantian noted. “All too often we see that women and minorities are less likely to be in the roles that lead to success, less likely to be reporting to supervisors who have clout, teams that are favored. There's a damping effect on their progress.”

Maybe? Millennials value flex work

A final variable the team looked at was the importance of flex work to millennials. Unfortunately, the criteria they had to work with were limited to status as a part-time employee and data on leaves of absences. Millennials employed as part-time workers and those who took long leaves of absence were both more likely to leave a company in the next year.

Still, these takeaways only scratch the surface of what's possible to do with the wealth of data employers have at their fingertips–and that data is going to be unique for each employer. “Simply relying on conventional wisdom, what you hear from others or see come out of surveys can be misleading,” warned Nalbantian. “It's important to take advantage of the data you are sitting on to understand your workforce in the deepest way you can.”

Read more: 

• 5 technology and data trends affecting employee benefits
• What does it take to make millennials happy with their careers?
• How data analytics can help you reposition benefits offerings