Thus, a woman's fertility begins to decline significantly after the age of 35. Spontaneous and successful pregnancies after the age of 40 become less common, and after the age of 45 are rare (but not zero!). The woman seeking natural conception at this age will find that the facts are fairly discouraging. While 80% of women between 40 and 45 can potentially conceive with different methods, this percentage falls off dramatically after the age of 45. The average woman notices that by this time her cycle is already less regular.
An externality is a consequence of an economic activity experienced by unrelated third parties; it can be either positive or negative. Pollution emitted by a factory that spoils the surrounding environment and affects the health of nearby residents is an example of a negative externality.
A positive externality (also called external benefit or external economy or beneficial externality) is the positive effect an activity imposes on an unrelated third party. Similar to a negative externality, it can arise either on the production side, or on the consumption side. Examples of positive production externalities include: 1  A beekeeper who keeps the bees for their honey. 2  A side effect or externality associated with such activity is the pollination of surrounding crops by the bees.