Abstract
In this article, the temporal progression of quality indicators in the Cambridge Structural Database is evaluated statistically as a simplistic and accessible measure for structural quality trends.
R
1 showed a strong decrease until 1980 followed by comparatively small changes, whereas
wR
2 increased significantly between 2000 and 2025. Residual electron-density extrema remained broadly stable, although the magnitude of the residual densities showed a small significant decrease. Exploratory normalization by unit-cell volume produced decreasing recent
R
1 and
wR
2 ratios, whereas
F
(000)-normalized
R
1 decreased and
F
(000)-normalized
wR
2 remained stable. Also, quality indicators are plotted on an elemental basis, and their trends are described.