Concentration indexes based on regional markets show that the Dutch market for refuse collection is highly concentrated in 2002 and 2010. Similar to earlier work in 2007, the results indicate some evidence that high concentration increases costs and therefore (partly) offsets the advantage of contracting out. In 2002, results with respect to concentration are somewhat less robust. In 2010, the cost-advantage effect of private provision becomes smaller. However, for this year, we have a stronger indication that the cost advantage of private provision depends negatively on regional concentration measured by the Hirschman–Herfindahl Index.