I've read in this article that the 3 valence quarks make up only 0.2% of the mass of a proton (or neutron) and the remaining 99.8% comes from gluons. From other sources we know that there are an infinite number of sea quarks popping in and out of existence, being created from and returning to gluons. Is it worthwhile to look at the contribution of these sea quarks as a source of mass, or do we just state that the gluons are the source of mass, regardless of the state they happen to be in at the moment?