The Nation article did not cite a specific reference, they were just talking about data so is this the right reference you should be looking at? I notice that they are talking about the top 10% of wage earners, not the bottom 90%. For example, they seem to be comparing the differences between between, say, the 90-100% group vs the 99.5-100% group. In that case, the 0-90% group is not covered there. I also don't see any of the other numbers quoted for the highest income wage earners (e.g. 599%). If nothing else, ask the authors.