Dear Cynthia Thank you for your quick response. I included a snippet of a table for the year 2019. This is an example of 1 tabel out of 5 I have, one for each year (2018, 2019, 2020, 2021 and 2022). So I have 5 tables like this where the variable name k_YEAR, in this case 2019, is my main indicator. In that column you can find around 150 observations consisting of productcodes. As you already suggested, these tables need to be matched on the observations in k_YEAR. You are correct that I was referring to an observation (in this case a six-digit number) and not to the variable name, sorry for my vagueness. The creation of a final table with unique product codes (observations under k_YEAR) is my goal. This table should be created under two conditions 1) if the productcode appears in 2022 (my most recent data point) then the productcode should automatically be selected regardless of the other years, and 2) for the remaining years (2018-2021) that productcode should only be selected if it appears in 3 out of the 4 years/tables. That means that a product should not be selected when it only appears in the tables for 2018 and 2019, thus only appearing twice as opposed to thrice. In the example you gave the product should automatically be selected because it appears in the 2022 data, my first criterium. I hope this clears up my question. If you have more, don't hesitate to ask.
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