What is data verification and why is it necessary?

"Data verification refers to checking to make sure data is accurate and consistent. Many times verification takes place when data is migrated or merged from external data sources. The reason it's important is because even small mistakes in data can result in huge problems and incorrect results. For example, if you're merging customer information and one of the columns of information gets accidentally shifted up or down, this can cause you to have incorrect information listed for every single customer. In my last role, I played a part in an ongoing verification process whereby periodically I would check to make sure the information we had recorded for the upper management of various companies was up-to-date and accurate. This was necessary because our product tracked CEO and management changes to aid our clients in their investment decisions."