A slew of political demonstrations this year has bolstered sales at local art stores.

At Blick Art Materials, General Manager Larry Aldrich anticipates the busy times when he needs to stock up, but this year brought an unexpected rush.

"I had twice as many people as I have ever had in my store on that day," said Aldrich.

It happened at the Seattle store in January, right before the Women's March. Customers were stocking up on poster board, pens, paint, and brushes. Aldrich watched people with different political views walk through the door.

"I mean the election was very exciting and very volatile, and there were a lot of people on both sides," said Aldrich.

What the customers had in common was they wanted to express themselves through art. It appears that was happening nationwide, based on retail sales.

The NPD Group, a company that interprets market trends, took note of the Women's Marches and found 6.5 million poster boards were sold in the U.S. during January. Nearly a third of that number were sold during the week of the Women's March.

According to the NPD Group, sales of poster board were up 33 percent, and foam boards up 42 percent compared to the same time last year.