There might be some objectivity to the words "serious bike rider". These words have to be defined and then you will be able to get somehwere on this.

One approach is to ask the question, Why are you riding. Another might be how many days do you ride in a year. Another would be how many hours do you ride in a given time period. Some of these would depend on factors like location, So Calif vs. Siberia.

Then there are conflicting terms like recreational vs. professional. I imagine that if you're a professional at this, its your livelihood and therefore your time commitment is high. Also a professional might not necessarily mean racing. There are professional messengers who ride bikes. In some Asian countries, there are bike type taxi's.