If Dividend Yield increases over time:
An increasing Dividend Yield may indicate either the amount of dividends per share have decreased compared to the stock price, or the stock price has increased compared to the dividends per share.
If Dividend Yield decreases over time:
A decreasing Dividend Yield may indicate either the amount of dividends per share have increased compared to the stock price, or the stock price has declined compared to the dividends per share.
If Dividend Yield stays the same over time:
An unchanged Dividend Yield may indicate the amount of dividends per share as compared to the stock price has remained the same.