Updated

Even with the U.S. economy booming and the job market strong, hiring has slowed among one category of employers: Small businesses.

Yet it isn't because these companies are hurting. Far from it. Small businesses today are generally optimistic, and most say they're enjoying healthy sales.

Rather, smaller companies are being hamstrung by the economy's very strength: Low unemployment has shrunk the pool of job seekers and intensified competition for workers. And smaller companies are in many cases losing out to larger employers, which typically can offer more generous pay and benefits. Some larger businesses are also using their financial muscle to poach employees from smaller companies.

Also contributing to the slowdown in hiring by small businesses is a more discouraging trend: Americans are forming fewer companies.