SEC利回りと分配金利回り
2つの利回り、2つの疑問：過去に何を支払ったか、そして現在何を稼いでいるか？
Trailing distribution yield answers 'what did this fund actually pay over the past year, relative to today's price?' It is backward-looking, includes every distribution type (some of which may be return of capital), and is the figure this site labels Yield TTM.
SEC 30-day yield answers 'what is the portfolio earning right now, after expenses?' — a standardized calculation the SEC requires, based on the last 30 days of portfolio income. For bond funds it approximates the forward-looking earning rate; for option-income funds it can be far below the distribution yield because option premium is not 'income' in the SEC formula.
Neither is wrong — they answer different questions. Comparing funds requires using the same measure for both, and knowing which one a website (including this one) is showing.