The preconditions for declines in this variable were memorably summarized by Ansley Coale in the dictum “ready, willing, and able.” In Gregory Clark’s Malthusian model, an upwards-sloping curve representing this variable appears on the top of two graphs. This variable can fall when quality dominates quantity (10[1])in a trade-off introduced by Gary Becker. A fall in this variable made France the first country to undergo a historical “transition” (10[1])that universally accompanies economic development. When this variable (10[1])is low, an “inverted pyramid” (10[1])shape (10[2])is generated (-5[1])on a common plot that shows age on the y-axis. South (10[1])Korea falls far below the “replacement (-5[1])rate” of this variable at around 2.1. For 10 points, name this variable that was sharply reduced by China’s one-child policy. (10[1])■END■ (10[2])