It was another difficult day on Wall Street.

The Dow Jones Industrial Average—an index of 30 large-cap stocks—fell 913 points to close at 19,173.98. That amounted to a 4.55 percent selloff.

Things weren't quite as bad on Bay Street in Toronto, where the S&P/TSX Composite Index dropped 319 points to end the day at 11,851.81.

In Toronto, today's decline amounted to 2.62 percent.

On the week, the S&P/TSX Composite Index sank 6.3 percent, compared to an 8.3 percent fall for the Dow.

But in a curious twist, Canadian investors with portfolios more heavily weighted American stocks may have fared better over the past five days.

That's because of a fairly steep drop in the Canadian dollar.

Take Apple as one example.

On March 16, it opened at US$241.95. Today, it had a brutal day, closing at US$229.24.

That's a 5.2 percent decline on the week. Ouch!

But let's say, for the sake of argument, that you are Canadian and held 100 Apple shares through this downward ride.

The story looks considerably different.

Today, those 100 shares would be worth CDN$32,854.68, based on the exchange rate at the close (US$1=CDN$1.4332).

At the opening on March 16, 100 Apple shares were worth CDN$33,786.90, based on the exchange rate on that day (US$1=CDN$1.3964).

That's a difference—in Canadian dollars—of just 2.8 percent.

That's far better than the 6.2 percent drop in the S&P/TSX Composite Index this week in companies listing in Canadian dollars.

(The exchange rates are from the Bank of Canada's website.)