query: SELECT ?item ?yaleid ?earliest ?latest ?averageyear WHERE {
    ?item wdt:P8583 ?yaleid ;
          p:P571 ?inceptionstatement .
    ?inceptionstatement ps:P571 ?inception ;
                        pq:P1319 ?earliest ;
                        pq:P1326 ?latest .  
     FILTER (wikibase:isSomeValue(?inception) && YEAR(?earliest) > 0 && YEAR(?latest) > 0 && YEAR(?earliest) <YEAR(?latest) )
    BIND((YEAR(?earliest)+YEAR(?latest))/2 AS ?averageyear)
    } LIMIT 10000
    