Here you find information how we calculate dividend yield.
Dividend yield is calculated as the annual dividend per share divided by the stock price per share.
Sources that don't focus mainly on dividend investors sometimes don't pay attention to the kind of dividend being paid and used when calculating dividend yield.
Some types of dividends are not to be used when calculating forward dividend yield. One such type is a Special Dividend. Special dividends are one one-time payments by the company and often don't repeat.
That's why special dividends should not be used when calculating foward dividend yield.