Q&A for professional and amateur woodworkers
select y_r, mm,cnt as curr,prev,round(100-cnt*100.00/prev,2) prc from ( select y_r, mm,cnt,lag(cnt) over (order by mm) prev from ( select year(creationDate) as y_r, month(creationDate) as mm, count(1) as cnt from posts where PostTypeId between 1 and 2 group by year(creationDate), month(creationDate) ) A ) A where cnt < prev order by y_r, mm