On Sunday, I read an excellent article,

Tantuh Macro: "The claim that 'U.S. stocks always decline significantly during each transition of Federal Reserve chairs' " is incorrect.
The maximum drawdown within the first six months after a Fed chair takes office, and the maximum drawdown within any six months in the history of the S&P 500, show no significant difference.
If the calculation method is based on the lowest point within six months of taking office minus the S&P 500 level at the time of appointment, then
1) The maximum drawdowns within six months after the appointment of the most recent seven chairs are as follows:
Burns (1970-02-01): 19.20%
Miller (1978-03-08): 0.00%
Volcker (1979-08-06): 4.25%
Greenspan (1987-08-11): 32.82%
Bernanke (2006-02-01): 4.58%
Yellen (2014-02-03): 0.00%
Powell (2018-02-05): 2.56%
The median is 4.25%
2) The distribution of maximum drawdowns within any six months for the S&P 500 is:
10th percentile: 0.09%
25th percentile: 1.44%
75th percentile: 8.98%
90th percentile: 16.24%
Median: 4.12%
The medians of both are almost the same.
In a t-test for the means being equal, p=0.2870; Wilcoxon test p=0.3438; no significant difference.
“In summary, according to historical patterns, the U.S. stock market almost always experiences significant declines within any six-month period. This is the norm in history, and it’s not surprising for the next six months either. It can even be inferred that, due to the historically high valuation levels of U.S. stocks, future declines may be larger than the historical median.”
(Based on the continuously increasing forward EPS, I personally do not think the current market valuation is very high.)
The original text can be searched as Tantuh Macro.