I really support differentiation . . . ranking employees into performance categories of top 20%, middle 70% and bottom 10%, and then managing them "up or out" accordingly. But don't companies face all sorts of resistance when they try to implement this system?

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"Resistance" may be too soft a word! Yes, differentiation has its advocates, and even its hardcore devotees, but no other management practice that we talk or write about ignites the same firestorm of controversy. So thanks for asking about it. Your question gives us a chance to sort differentiation myth from reality. Done right, differentiation is not, for instance, 'rank and yank', with its purported public firings of stunned victims once a year. Nor is it cruel, corrupted by favouritism and culturally inappropriate.

What is it, then? Very simply, differentiation is based on the principle that the team with the best players wins. If you don't agree with that, differentiation will never make sense to you. But if you do, differentiation provides a method for making that principle spring to life. How? By rewarding stars in an outsized way, in their souls and their wallets, by actively developing "the middle 70" with training, and by moving out bottom-tier performers so better talent can be brought in. Basically, differentiation is a way to build meritocracies and raise the performance bar.

So why does it spark "all sorts of resistance", as you so accurately suggest? By far, the most common reason given is that differentiation is cruel. But we'd make the opposite case. Because of performance appraisals, people always know where they stand. Maybe the news is not always good, but it allows them to control their own destinies.

Compare that to companies where managers, in the name of kindness, allow people to putz along for years with a pat on the back. Then a downturn occurs. Middle-aged underperformers, of course, are always first to get the axe.

The employee, years earlier, might have been able to find a job with a future. Now, at 45 or 50, he must enter a job market more competitive than ever. That's cruel.

The 'yank' myth is that the bottom 10% are summarily fired. In reality, that's rare. More typically, when a person has been in the bottom 10% for a sustained period, their manager starts the conversation about moving on.

Confronted with the cold reality of how the organisation views them, most people leave of their own accord, and often end up at companies where their skills are a better fit.

Moving on to resistance reason number two: that differentiation spawns favouritism. The top 20%, it's said, will always be the insiders. It's possible. But favouritism is a risk in any evaluation system. At least differentiation's performance reviews are a countervailing force.

A third common criticism is that the continual removal of the bottom 10% forces managers to push out good employees. But if that thinking is right, why do championship teams replace the bottom of their roster every year? Because the best organisations believe performance can always improve. And everyone knows teamwork is part of what makes someone a star.

The final reason people resist differentiation is that they believe it won't work in their company's unique culture.

We've heard this from people at companies small and large, Japanese, Swedish and Mexican companies, growing companies and shrinking ones too. But in reality, we've seen differentiation implemented everywhere. In some situations, it just takes more time. But differentiation should never be rushed anyway. People have to get used to candid feedback and the concept of pay for performance.

We're certainly not going to claim that differentiation is perfect. But we know of no better way for companies to build great teams. And neither, we have found, do its critics!

Jack and Suzy Welch are the authors of the international bestseller, Winning. They are eager to hear about your career dilemmas and challenges. You can email them questions at Winning@nytimes. com. Please include your name, occupation, city and country.