The evidence for dimensional reduction has come mainly, although not exclusively, from calculations of the spectral dimension. The spectral dimension is a measure of the effective dimension of a manifold at different resolution scales. Early numerical simulations within the causal dynamical triangulation (CDT) approach to quantum gravity found a spectral dimension of 4.02 ± 0.10 at large distances and 1.80 ± 0.25 at small distances. This result created significant interest in dimensional reduction within the quantum gravity community. A more recent study of the same point in the parameter space of CDT found consistent results, namely 4.05 ± 0.17 at large distances and 1.97 ± 0.27 at small distances.