Here’s a sign of a slightly improving economy: It appears some companies are starting to worry that employees - many of whom have endured several years cutting budgets and perks while adding workload - will jump ship.

About 40 of the approximately 100 human resources executives recently polled by outplacement firm Challenger, Gray & Christmas said they are growing more concerned that competitors will poach their top workers as the economy improves.

About half said that’s always a concern, even in a recession. But you can’t necessarily do much about it when the economy is in the doldrums. About 60 of the 100 companies polled said they had to reduce or eliminate employee perks due to the recession.

Now, with the economy slowly improving, about 40 of the HR executives said they are bringing some perks back, and nearly 20 said they have reinstated all of them. About 25 have introduced new perks.

We hear a lot about low-cost ways to make employees happy, but HR professionals appear to know a new coffee machine isn’t going to make your best salesperson stick around. Nearly 80 of the 100 said performance bonuses – that’s right, cash – is the best way to keep the most talented workers from moving on. A 401(k) plan, vacation or personal time and flexible schedules also ranked high among ways to retain the most talented workers.

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