Sure buddy. Its not like people had statistics in the 1929. Oh wait…
The deflationary period began in 1927. Long, long before Black Friday. Deflation then grew out-of-control over the next few years, leading to 30%+ unemployment numbers (because as we all know, deflation causes unemployment).
After the 1930s, this country pretty much swore off deflation ever again. We have done our best to avoid deflation, for good reasons as the graph above should make obvious.