Superposed-epoch plot of the R_i index obtained by aligning all solar cycles 0–23 on their R_i = 25 crossing point in the final decaying phase of the cycle (NB: Curves are numbered according to the cycles preceding and following the minimum). This representation allows us to compare directly the length and depth of the solar minima. Thick lines highlight the 22–23 minimum (green) and the last minimum 23–24 (red). The four shaded boxes mark four families of cycles according to the steepness of the rise following the minimum: fast, moderate, late and weak (top to bottom).