Comparing previous years data

[JGlennH]

I am what I consider a novice Excel user, so I might not describe this perfectly.  I have several years of sales performances that I want to merge into one so I can analyze to see how many new customers bought product and how many existing customers dropped off of the new spreadsheet.  How do I do this?

[#2]

@JGlennH That's a broad question. How do  you "have" the data? Easiest would be if you have three columns (Date, Customer, Sales Amount). Then you can make a pivot table, summarising sales by customer by year. It would enable you to identify both new customers and ones that no longer buy,

Novice or not. It would be good to learn about pivot tables.

[#3]

@Riny_van_Eekelen 

Thank you for the advice!  I do need to learn how to make pivot tables.  I use them when others have created the spreadsheet, but I have not had to make one myself.  I appreciate the help!