Dividend yield is a tough thing to track because it's a moving target. Dividends are paid periodically the yield is calculated based on the stock price when the dividend is declared (usually, though some services may update this more frequently).
I like to calculate my own dividend by annualizing the dividend payment divided by my cost basis per share. As an example, say you have shares in X, Co. X issues a quarterly dividend of $1 per share and the share price is $100; coincidentally this is the price at which you purchased your shares.
$1 x 4 = $4 (times four because quarterly of quarterly frequency)
$4 / $100 = 4%
But a few years goes by and now X issues it's quarterly dividend of $1.50 per share, and the share price is $160.
$1.50 x 4 = $6
$6 / $160 = 3.75%
However your shares only cost you $100.
$1.50 x 4 = $6
$6 / $100 = 6%
Your annual yield on X is 6%, not the published 3.75%. All of this is to say that looking back on dividend yields is somewhat similar to nailing jello to the wall. Do you look at actual dividends paid through the year divided by share price? Do you look at the annualized dividend at the time of issue then average those? The stock price will fluctuate, that will change the yield; depending on where you bought your stock, your actual yield will vary from the published amount as well.