It also depends on how the data is being used. For this study source of wages is being heavily weighted as well as what companies an individual chooses to invest in. So while household is the focus of the headline companies are more the focus, since by the metric used it seems as though someone who lives a green life style on paper living in a tent and biking but invests majority of their money and sees it grow would be a heavier polluter than someone who makes less but lives in a big house, drives suvs and pick ups, but doesn't see their net worth increase with most money not being used towards investments but paying off debt.