Mean number of quality identifiers (QI) for articles in 5-year blocks.
| Year of Publication | Dichotomous, n = 22 (max QI = 9) | Polytomous, n = 93 (max QI = 10) | ||
|---|---|---|---|---|
| No. of Articles | (Mean ± SD) | No. of Articles | (Mean ± SD) | |
| 1991–1995 | 0 | 1 | (3) | |
| 1996–2000 | 0 | 10 | (3.3 ± 1.3) | |
| 2001–2005 | 8 | (3.4 ± 0.8) | 21 | (3.4 ± 1.9) |
| 2006–2010 | 12 | (4.7 ± 2.0) | 40 | (6.6 ± 1.9) |
| 2011–2012 (1st 14 mo only) | 2 | (6.5 ± 2.1) | 21 | (6.9 ± 2.3) |