Bureau of Labor Statistics has been collecting data since the 1930's or so. Looking at long-term graphs is interesting. For example in this one there appears to be decreasing frequency but a constant max amplitude.

3 Months Net Change
Series Id: CES0000000001
Seasonally Adjusted
Super Sector: Total nonfarm
Industry: Total nonfarm
NAICS Code: N/A
Data Type: ALL EMPLOYEES, THOUSANDS

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