The headline index of confidence fell to 80.0 in August from July's 85.1 reading. Economists had predicted a tick up to 85.2.
The sub-index of economic conditions fell to 91.0 from 98.6.
The economic outlook sub-index fell to 72.9 from 76.5.
Inflation expectations one year ahead were unchanged from July at 3.1%.
Inflation expectations five years ahead were unchanged at 2.8%.
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