First post on this forum so I hope to explain my question appropriately.

Our company issues catalogs to 3,000 customers. The products in this catalog have a 4 year life span. Historic sales indicate that only 1/3 of the distributed catalogs will produce a sale. Of those sales 33% come in year 1, 27% come in year 2, 22% come in year 3 and 18% come in year 4. If a customer does not buy in year 1, what is the probability they buy in year 2? If they don't buy in year 1 or 2, what is the probability they buy in year 3 and so on.

I thought a customer will always have 1/3 probability to buy at anytime in the 4 years but something tells me that as the products in the catalog grows old and out of fashion, the probability reduces year over year as indicated buy the decline sales.

Thank you far any help anyone can pass along