Premium/discount and Z-scores

Premium/discount = (market price ÷ NAV − 1) × 100. Negative values are discounts. The headline figure on a fund page is indicative when it pairs a newer price with an older NAV (labelled, both dates shown); the contemporaneous figure pairs the closing price with the NAV published for the same date and is what every statistic and ranking uses.

History uses daily pairs only where both a close and a NAV exist for that date. NAV is never forward-filled; missing dates are simply absent.

Averages are arithmetic means of the daily pairs over the last 3, 6, 12, 36 and 60 calendar months. Standard deviation is the sample SD (n − 1).

Z-score = (contemporaneous premium/discount − window mean) ÷ window SD. Minimum observations: 40 (3m), 80 (6m), 160 (1y). No value is shown below the minimum or when SD is zero. A negative Z-score describes a wider-than-usual discount for that fund; it is not a valuation opinion.

NAV source. Daily NAV from the Nasdaq NAV symbols (X<ticker>X) via Tiingo. A symbol is accepted only after a consistency test against the fund's own closing prices (median |price ÷ NAV − 1| under 40% and a standard deviation under 15 points over the past year — a wrong fund fails this). Where the feed's name for the symbol differs from the fund's current or SEC-recorded former names, the mapping is retained but flagged for editorial review and shown as “unverified mapping” on the fund page. Sparse official NAV facts from SEC XBRL supplement the series.