What Is a Fund's 30-Day SEC Yield?
Before this particular figure existed, comparing the yield on two bond funds meant comparing two numbers that might have been calculated in entirely different ways. A standardized formula was created specifically to close that gap.
The short answer
A fund’s 30-day SEC yield is a standardized calculation, required by regulators for funds that want to advertise a yield figure, based on the fund’s net investment income over the most recent 30-day period, annualized and divided by the average share price during that period. Because every fund uses the identical formula, it allows a more apples-to-apples comparison between funds than each company’s own choice of yield metric would allow on its own.
Why a standard formula was needed
Before this requirement, a fund company could choose almost any method to describe its yield, and there was little to stop one firm from picking a flattering calculation while another used a more conservative one. The 30-day SEC yield formula was set specifically so that every fund reports the same thing, calculated the same way, over the same length of time. That consistency is the entire point of the figure — not that it’s the most generous or most accurate number possible, but that it’s the same measuring stick applied everywhere.
What goes into the calculation
- Net investment income. The formula starts from the interest and dividend income the fund’s holdings generated during the period, after subtracting the fund’s expenses, including its expense ratio.
- A 30-day window. Unlike a distribution yield that might be based on the most recent monthly or quarterly payout, this figure is recalculated using just the trailing 30 days, so it updates more frequently and reflects more current conditions.
- Average share price. The income figure is divided by the fund’s average net asset value over that same 30-day period rather than a single snapshot price.
What it leaves out
The 30-day SEC yield generally excludes capital gains, return-of-capital distributions, and other one-time or non-recurring items, focusing narrowly on ongoing income production. That makes it a useful tool for comparing the income-generating potential of similar funds, but not a complete picture of total return, which also depends on price changes and any gains distributed separately. A fund with a modest SEC yield can still deliver a strong total return if its holdings appreciate in value.
How to use it when comparing funds
Because the formula is standardized, it’s most useful for comparing funds that hold similar types of bonds against each other rather than comparing a bond fund to a stock fund, where the concept applies differently. Pairing it with distribution yield gives a fuller sense of both what a fund recently paid and what its current holdings are generating on an ongoing basis, since the two figures answer related but distinct questions.
A practical habit
When comparing bond funds, checking the 30-day SEC yield for each one, rather than relying on a single advertised number, helps make sure the comparison is genuinely apples-to-apples. It’s a narrow, technical figure by design, but that narrowness is exactly what makes it dependable for lining funds up side by side.