Upper panel: Model for the inter-glitch evolution of $\dot{\nu }$ from glitch j to glitch j + 1. The solid black line depicts the observed inter-glitch evolution. Assuming that the recovery of the glitch offset in the internal torque is completed at exactly the time of arrival of the next glitch, the observed glitch step ($\mathrm{\Delta }{\dot{\nu }}_{\mathrm{j}}$) in the spin-down rate is the sum of the permanent part ($\mathrm{\Delta }{\dot{\nu }}_{\mathrm{per}\mathrm{j}}$) and the recovering part ($\mathrm{\Delta }{\dot{\nu }}_{\mathrm{ig},\mathrm{j}}$) under ${\ddot{\nu }}_{\mathrm{ig},\mathrm{j}}$ due to the internal torque, as shown in blue. Subtracting the contribution of the internal torque from the total observed ${\ddot{\nu }}_{\mathrm{obs},\mathrm{j}}$ gives ${\ddot{\nu }}_{0,\mathrm{j}}$, the slope of the purple line, due to the external torque. The permanent shift ($\mathrm{\Delta }{\dot{\nu }}_{\mathrm{per},\mathrm{j}}$) is only partially counteracted by an amount ${\ddot{\nu }}_{0,\mathrm{j}}{t}_{\mathrm{g},\mathrm{j}}$, as shown by the purple line. The combined effect results in a remaining decrease in $\dot{\nu }$, with an inferred slope of ${\ddot{\nu }}_{\mathrm{long}-\mathrm{term},\mathrm{j}}$ (orange line). Lower panel: Long-term evolution over many glitches, shown in orange. This implies an effective negative ${\ddot{\nu }}_{\mathrm{long}-\mathrm{term}}$ and a negative effective braking index, given by the slope of the red line.