FYI: Historically, they have not been major occasions for selling.
Regardless of what happens, investors may not need to worry too much, as past shutdowns haven’t corresponded with significant stock-market selloffs. Data show that markets have seen modest weakness during shutdowns, with the S&P 500 SPX, -0.16% falling an average of 0.6% over the period of the closure, according to data from LPL Financial. The benchmark index was only positive in 44.4% of the 18 shutdowns going back to 1976.
Regards,
Ted
https://www.marketwatch.com/story/heres-how-the-stock-market-has-handled-past-government-shutdowns-2018-01-16/print