The Center for Housing Policy, an affiliate of the Washington-based advocacy group the National Housing Conference, has released its annual Housing Landscape report. Among other things, it reports that 26.4% of working renters spent more than half of household income on housing costs in 2011. The report defines a working household as one with an income less than 120% of the median for its area, and with members working at least 20 hours per week on average. Nationally, working renters saw their housing costs rise by 6% from 2008 to 2011, while their household incomes fell more than 3%.
You can see the complete Housing Landscape 2013 here.