Changes in incentives: suppose the commissioner of the national football league (nfl) institutes a rule requiring players to wear a new, lighter helmet that is designed to reduce head trauma during collisions between players on the field.
while the new helmets the probability of a concussion resulting from each individual collision, at the same time, the new helmets could also give football players an incentive to play more which could potentially the amount of violent collisions and thus the number of concussions suffered by nfl players, all else equal.

Reduced/depressed

courageously/daringly

Boost/inflate

Explanation:

The following statement displays the recommendation of National Football League's(NFL) rule to wear new and lighter helmets by the players to diminish the chances of head injury during collisions between players. However, it has led the players to play more brazenly and fearlessly that eventually may cause the expansion of the number of collisions suffered by NFL players due to the valiant behavior of the players. This equates the ratio and leading to no improvement in the reduction of injuries among them even after this rule.

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explanation: