A pronounced gender split is emerging in the 2016 U.S. presidential election. Based on national polls in October, Nate Silver writes, “on average, Clinton leads Trump by 15 percentage points among women while trailing him by 5 points among men. How would that look on the electoral map?” Silver does a quick-and-dirty estimation by adding or subtracting 10 points to/from the FiveThirtyEight forecast. Moving 10 points to Clinton’s column approximates what the electoral map would look like if only women voted:

Moving those 10 points to Trump’s column approximates the results if only men voted:

You’ve almost certainly seen these maps make the rounds of social media. This is where they came from and how they were made.