A government shutdown is looming. Here’s what history says could happen to stocks.

1. Congress faces an Oct. 1 deadline to pass funding or face shutdown. 2. Past shutdowns have coincided with S&P 500 gains, despite federal furloughs. 3. Recent research shows a 56% chance of a government shutdown. 4. Negotiations on healthcare subsidies could affect future funding agreements. 5. House Republicans plan to vote to avert shutdown by Friday.