Final answer:
Retailers review history or what sold last year during the step of analyzing retail sales data in the CTC process.
Step-by-step explanation:
During the CTC (Census, Trade, and Consumer) process, retailers are most concerned with reviewing history, or what sold last year, during the step of analyzing retail sales data. This step involves examining sales figures and trends from the previous year to determine which products were successful and which ones were not. Retailers use this information to make informed decisions about inventory management, purchasing, and marketing strategies for the upcoming year.