The following SQL query will give you a total count of cases for each individual user in CRM 2016 since April 1st 2015. You can change the date range with the following line: WHERE ca.CreatedOn > ‘DATE HERE’

SELECT us.fullname,
COUNT(*) as [Total Count]

FROM SystemUserBase as us with (nolock)
LEFT JOIN IncidentBase as ca
on us.SystemUserId = ca.OwnerID

WHERE ca.CreatedOn > '2015-04-01'
GROUP BY us.Fullname
ORDER BY [Total Count] desc