This is currently less than 1%. So it is a rare phenomenon, but in the aggregate of billions of human beings this is still a considerable number. The reasons for its occurrence are commonplace. It is just that the solution to leave is infrequent compared to working as best one can to surmount the problems and at least to survive until the body gives out, and fight the good fight, so to speak. In most cases, the needs of the being to handle its own problems come what may, even under dire circumstances of dishevelment and suffering, make the need quite compelling to complete the experience, even if it is quite a painful life. There is much gained from the karmic consequences of undergoing an ordeal, and even failing in the end, to overcome the accumulated difficulties of the kind that warrant a walk-in solution. Sometimes the decision is a close call, and the need of the walk-in become an overriding factor to make this not only acceptable, but a desirable choice for the person leaving, as well as their soul group, who must welcome the walk-in. So every situation is different. There are many needs, many agendas involved. The overall purpose of life is for growth and expansion. When growth stalls out, and there is more a contraction of soul expression underway, there is little served by prolonging the deficit and the agony. So in most cases, if there is an interested party to do a swap, it will be embraced by those involved, and then will move forward, and make a contribution to help all who are taking part, and that is the purpose after all, to provide a solution to a bad situation in progress.