An ex-dividend date is when a company's shares stop trading with its current dividend payout in preparation for the company to announce a new one. Usually, a company's ex-dividend date falls one business day before its record date. Investors should keep this in mind when purchasing stocks because buying them on or after ex-dividend dates does not qualify them to receive the declared payment. Newly declared dividends go to shareholders who have owned that stock before the ex-dividend date. Typically, companies will announce and implement new dividend yields on a quarterly basis.

Over the past year, Imperial Oil has seen its dividend payouts climb upward and its yields trend downward. Last year on June 3, 2020 the company's payout sat at $0.22, which has since increased by $0.05. Imperial Oil's dividend yield last year was 3.91%, which has since decreased by 0.72%.
Companies use dividend yields in different strategic ways. Some companies may opt to not give yields altogether to reinvest in themselves. Other companies may opt to increase or decrease their yield amounts to control how their shares circulate throughout the stock market.