Assuming that everyone uses asphalt shingles, which is definitely not the case. For example, the German Wikipedia article for asphalt shingles describes them as "a typical GDR roofing". Germans tend to prefer clay/ceramic tiles on their homes, which can easily last 50 years and more.
The asphalt shingles are very popular in the USA, which is what I assumed their first market would be, since contractors apparently have to be trained in their installation.
Thus at least 5% of the total roofing market in existing residential houses, is a potential customer each year.