instruction: what were the four most common specimen tests ordered since 2104?
response: SELECT t1.spec_type_desc FROM (SELECT microbiologyevents.spec_type_desc, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM microbiologyevents WHERE STRFTIME('%y', microbiologyevents.charttime) >= '2104' GROUP BY microbiologyevents.spec_type_desc) AS t1 WHERE t1.c1 <= 4