Reducing the minimum age for full-time missionary service from 19 to 18 for men is a tweak. But reducing the minimum age from 21 to 19 for women is a game-changer.
There will be a noticeable uptick in the number of men serving, after the initial big surge of 18 and 19 year-olds going out together, and coming back together.
However, that post-surge uptick in men would, to my logic, be limited to the number of men between their 18th and 19th birthdays who would otherwise go inactive or have worthiness issues during that year. (Though those with worthiness issues could still resolve them and go later, I’m thinking there may be some who get discouraged by the issue and still don’t go.)
I’m thinking that the “lost boys” who will now be “saved” by going at age 18 may be somewhere between 10 and 30%. (There is also the “logistical” factor, where for some it will be more convenient to serve at 18 instead of 19, but that is already done in other countries, and I don’t think it is a significant factor in the US, maybe a percentage point or two.)
But for women, as the age has been lowered by TWO years instead of one, that gives ALL of the worthy women an opportunity to serve an 18 month mission before the former minimum of 21 is reached. At age 19, assuming their boyfriends are the same age, those boyfriends will be on missions, and they can still get married at 21 if they want.
Therefore, I believe the increase in sister missionaries serving may be on the order of 100% to 200%, and theoretically even more.
I think the unspoken reason for the lowering of the age for guys is to “save” those who would otherwise go inactive or get discouraged between age 18 and 19.
But the fact that the age for sisters was NOT reduced by the same one year speaks volumes. THAT is going to have the bigger impact on the number of missionaries serving.
The change in age for women also requires new and earlier planning in terms of deciding to go or not go on a mission, especially as it relatess to cheduling college for young women in their junior and senior year of high school, along with new decisions/planning for their parents. “jks” wrote a good comment at Millennialstar that illustrates the new logistics for women.