I take the last quoted sentence to mean that the minimum wage "...would have reached $21.72...", not that it did reach that. Clearly, it didn't. The author was

I take the last quoted sentence to mean that the minimum wage "...would have reached $21.72...", not that it did reach that. Clearly, it didn't. The author was illustrating the overall decline in purchasing power of the inflation-adjusted minimum wage, despite its nominal increase. Hence the economic decline experienced by minimum wage workers.