[nickff]

I think you are right that those blogs do not fully explain what happened after 2003. It seems like the measured wealth dip (amongst all groups) from 2007-current is quite consistent with losses due to the drop in housing prices from the great recession (though I have no solid data to back this up). Lower income households tend to have a greater proportion of their wealth tied up in housing (and with less home equity due to a variety of factors including low down payments in those years), so they were likely disproportionately (negatively) impacted.

I am not sure what could explain the changes between 2003-2007, though I would be very interested to hear any ideas.