In fact, the prevalence of the grey economy should mean that Southern Europeans are working harder than the data suggests, although this is not an argument likely to impress Northern Europeans.
Of course, Southern Europe has its problems, and its history of corrupt leaders and authoritarianism have left legacies that continue to hold the region back. But the broad picture some Northern Europeans wish to believe in, of lazy Mediterraneans exploiting their virtuous neighbours, is based entirely on ignorance.