It’s only in the past few years that “two or more” races became an option on most demographic forms. Even into the early 2000s most demographic forms only let you pick one category so you had to make a choice. The 2024 number may more accurately account for mixed race people but there is no way that 80s number does at all.
Source: was a confused mixed child asking adults which I should pick on official forms and just got shoulder shrugs and hand waving from them.