How many people are really shopping for a gym?

This page plays out one made-up town, one month at a time. Every adult in town is always in one of these groups: your members, members at other gyms, on a trial, or not in a gym. The dots in "Every adult in town" show those groups.

Every month, the same six things happen, in this order:

1. Some members quit. Your gym loses the share you set in "Your members who quit each month". Other gyms lose the share in "Other gyms' members who quit each month".
2. Some of those quitters look for a new gym right away. That share is "Gym quitters who shop for a new gym right away". They will not go back to the gym they just left. Everyone else who quit stops going to a gym for now.
3. Some people who are not in a gym start looking. That share is "People not in a gym who start shopping each month". It is small, but there are a lot of these people, so it adds up.
4. Everyone who is looking books a trial somewhere. These are the "shoppers". Every gym in town splits them.
   • In Every shopper mode, "Your pull vs. each competitor" decides your slice. At 1x a shopper is as likely to pick you as any one competitor. At 2x, twice as likely. At 0.5x, half as likely.
   • In Fixed for my gym mode, you type how many trials your gym books each month. The page then shows how much pull you would need to get them. If there are not enough shoppers, you get as many as there are.
5. Last month's trials end. The share in "Trials that become members" join that gym. The rest leave.
6. People who left a gym take a break from it. Someone who quit a gym, or tried it and did not join, will not book that same gym again for the months in "Cool-off before a gym can rebook them". They can still try any other gym. When the break ends, the share in "Who become open to that gym each cool-off" are open to it again. The rest wait another break. The model only remembers the last gym each person left.

Two switches:

• "Link to Share of town in a gym" picks the number of people who start looking each month for you, so gyms win about as many members as they lose. That keeps the share of town in a gym about the same over time, like most real towns. Turn it off to set both numbers yourself.
• "When a member quits" lets quitters go straight back to the open market instead of taking a break from their old gym.

The point: in any month, only a small group of people in town are looking for a gym, and every gym is fighting for that same small group. Growing means winning a bigger slice of it, or keeping members longer.

This is a model to show the trend, not a forecast. The shape matters more than the exact numbers.