Do we group by job position, skill level, education, experience? And what is "same experience"? In tech, it is usually counted in years, regardless on how many hours you work during the year. Compare to airline pilots where the metric is flight hours. The same kind questions can be asked for all other points. Even the wage can be tweaked. Is it by year? working day? hour? What about pauses, overtime, work at home, commute time, ...

By carefully choosing the metrics, we can say whatever we want.