They may not have changed as much to model what customers want as online shopping platforms for retail products, but private benefits exchanges are gradually evolving in response to employer and employee needs in choosing customized benefits.

That’s according to a report from the Society for Human Resource Management, which finds that private benefits exchanges—commercially marketed platforms on which employees can shop for a wide range of employer-sponsored health and voluntary benefits—are slowly growing and changing in response to market demands.

Not that many businesses have shifted to private exchanges—typically administered by a benefits broker or consultancy—in providing benefits, with consultancy Accenture reporting that only 8 million people were enrolled in health coverage through a private exchange. That’s a 35 percent increase over the year before, but it hasn’t yet caught up with previous, far more optimistic predictions.