Interesting ideas. I suppose we can say the US job market is healthier than Spain's, because unemployment in the US is low, and the pay/expense ratio is good enough. In Spain, unemployment is very high, and the pay/expense ratio is not very good.
But imagine if the US job market changed to this scenario: still the pay is high, still the expenses are low, still the jobs are available, but you have to change jobs every week. That would signal two things:
1) Employers are suddenly finding it advantageous to rid themselves of workers on short notice
2) Time and money are being wasted interviewing people and onboarding them rather than letting them work for sustained periods
I think such a system, while still "healthy" because workers are still employed and paid similarly, is "less healthy" than a system where the workers can expect the duration of their work at one employer to be longer than 1 year