Nothing defeats the point of using an earned value system as quickly as managing to achieve zero variances.  Again and again, I have watched good systems lose valuable information by continually tweaking the system or data to remove variances due to management or client pressure.  When used as the tool it is intended to be, variances provide the project team, management and end client valuable information.   Virtually every project will have some variances, it is how those variances are managed that impacts the project.  When variances occur, the cause should be identified, the impacts of the variance on the project schedule and/or budget should be assessed, and any potential opportunities for recovery of the variance should be identified, evaluated and implemented where possible.  This information should be reviewed with the project team and management team on a regular basis until the impacted work is complete or the variance has been recovered.