SQL Trends - SQL Server Read/Write Ratio

SQL Server Read/Write Ratio :

SELECT   
CAST(SUM(user_seeks+user_scans+user_lookups) AS decimal)/CAST(SUM(user_updates)+SUM(user_seeks+user_scans+user_lookups) AS decimal) 
AS ReadPercent 
, CAST(SUM(user_updates) AS decimal)/CAST(SUM(user_updates) + SUM(user_seeks + user_scans + user_lookups) AS decimal)  
AS WriteRatio 
FROM sys.dm_db_index_usage_stats

Ref : Is 80/20 a nineties estimate?