Historic comparison offers some cause for optimism.

与历史相比较，人们可以从中找到某种感到乐观的理由。

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Americans, only a decade ago after enjoying low unemployment, historic economic growth and unrelenting optimism, are now ecstatic to find even part time work.

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Nonetheless, optimism remains more than one standard deviation above its historic average of 39%-a sign that it remains at high levels.

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