Does that include public sector workers? If so, countries with a large public sector will show long average tenures even if the rest of the economy is based on hire and fire principles.
Americans, do you consider this a strength or a weakness of your economy?
A huge strength. A ability to leave a job easily, or to be fired easily, is also the ability to get a job easily.
Closed systems don't allow for mobility. Guaranteed employment, from a company's perspective, adds huge barriers to hiring.