Relative costs of unemployment versus inflation
Unemployment: deflation produces unemployment, and can create a deflationary spiral that leads to an employment crisis.
Deferred consumption: when prices fall, consumers wait for them to continue falling before buying, leading to a fall in AD,
Falling consumer confidence: as prices fall, consumers feel the value of their goods drops, and tend to consume less.
Investment: during deflations businesses earn less revenue, so there is less business confidence.
Cost to debtors: anyone who has taken a loan suffers as a result of deflation, because the value of their deb rises. SInce revenue is low, businesses may have difficulties paying loans and go bankrupt.