query: select ?qualvalue ?quallabel (count(?qualvalue) as ?total) where {
  ?item wdt:P31/wdt:P279* wd:Q355304 .
  ?item p:P625 ?statement .
  ?statement pq:P518 ?qualvalue .
  optional { ?qualvalue rdfs:label ?quallabel filter (lang(?quallabel) = "en") . }
  } group by ?qualvalue ?quallabel order by desc(?total)