Left: spin-down power Ė and characteristic age τc of pulsars with a firmly identified PWN, candidate PWN, and without TeV counterpart (grey dots). The black line and shaded band show the injection evolution of the modelling used in this paper. The dashed lines indicate lines of constant total remaining energy Ė τ; see Appendix B. Hence a model curve that starts at Ė₀τ₀ = 10⁴⁹ erg represents a pulsar with total initial rotational energy of 10⁴⁹ erg. Since both Ė and τc depend on P and Ṗ , the axes in this plot do not represent independent quantities. Right: same data, shown in the commonly used view, using the independently measured P and Ṗ .