GRE Logical Reading: ETS-GRE逻辑单题ETS - 7I4F9KW0GKJ1DHA7K$

Each year a consumer agency ranks all domestic airlines for on-time performance during the previous year, using as its sole criterion the percentage of each airline's flights that left no more than fifteen minutes late. The agency does not count delays due to mechanical reasons, but the fact that the percentage of delayed flights hat were delayed for mechanical reasons was approximately the same for all domestic airlines last year means that ______.