What was the most common type of approach for summarization before 2002?
SELECT ?approach ?approach_label
WHERE {
  orkgr:R6948 orkgp:compareContribution ?cont.
  ?cont orkgp:P15 ?implementation.
  ?implementation orkgp:P5043 ?approach.
  ?approach rdfs:label ?approach_label.
}
ORDER BY DESC(COUNT(?approach_label))
LIMIT 1