premise: Promotus Advertising, (from Latin Promotus, meaning: "to advance (someone) to a higher grade or office"; "to move forward, advance"; "to further the growth or progress of (anything).") located in Indianapolis, Indiana, was started in 1983 by Bruce Bryant during a time when there were very few African Americans working in the advertising business and no African American owned agencies.
hypothesis: A few black-owned ad businesses existed in the 1980s.
reason: The text tells us "in 1983... a time when there were very few African Americans working in the advertising business and no African American owned agencies" - so we can infer that in this time period, the '80s, there were none. The algorithm confused working in and owned by blacks, or it confused African Americans.