They found that the number of close friends (that inner 5-layer) remained remarkably stable at six individuals, but the number of best friends (essentially the sympathy group 15-layer) declined with age, and this was true of both ethnic groups. This again suggests that, as we age, we tend to sacrifice less close friends in order to invest what time

used the average number of different people phoned during a month (essentially the sympathy group, or 15-layer) to explore changes in network size with age.

average network size was around 125, with a distinct ∩-shape against age: networks initially increase in size as we age, reach a peak between the mid-twenties and early thirties and then decline steadily into old age