Pull out repeating customer numbers for consecutive years

I have attached a simple workbook that contains the customer id's for all customers for a particular year. I then did a simple conditional formatting to give me which ones are duplicate (highlighted in red). What I would like to be able to do is to determine which customers are repeat customers and summarize those numbers in a separate column, if that makes sense. So, if there customer number shows up in all 3 data columns, then they would be a candidate to go in the return customer column. I do not know a swift way to do this. Thank you all for considering my post.

I sorted the 3 columns individually (just to make checking easier) and given customer numbers in a column are not repeated

In Column D

=COUNTIF($A$2:$C$853,A2)

copy down

This checks 2014 customers (longest lis) and will give count of 3 if they are all 3 years

You can then filter on the "3"

Will this work for you?

John,

This will work perfectly. Thank you again for your help!

You are very welcome.

Thank you for the feedback and rep.