Probability of non-degrading herd status over a 5-, 10-, and 15-year period according to the initial herd status (in lines). The figure shows only selected scenarios (16), sorted by their overall rank. Parameter values are shown as circles. Parameter of reducing calf exposure (C_EXPOSURE) has four possible values ranging from 0.35 (optimal, plain circle) to 1.0 (standard, empty circle). Other parameters (test frequency as T_FREQUENCY, and culling proportion as T_%CULLPOS) have only two possible values (see Table 1). Scenarios with the best overall ranks are on the left, scenarios with the worst ones on the right.