Menstrual synchrony by chance when there is menstrual cycle variability. Yang and Schank argued that when there is cycle variability (i.e., either women have irregular cycles, have cycles of different frequencies, or both), most women will have the opportunity to experience synchrony even though it is a result of cycle variability and not a result of a mechanism such as the exchange of pheromones. For example, consider two women A and B. Suppose A has menstrual cycles that are 28 days long and B has cycles that are 30 days long. Suppose further that when A and B become close friends, B
Menstrual cup spillage. During peak flow, most women use two disposable cups per day. Reusable menstrual products (including menstrual cups, but not disposable menstrual cups) are more economical than disposable products. Money will be saved using a menstrual cup, compared with other options such as tampons. A woman in a developed country spends an average of US$60 per year on pads and tampons. If a woman menstruates for 40 years, the lifetime expense for pads and tampons is US$2,400. If the average silicon menstrual cup lasts between one and five years, then between eight and 40 would be needed in 40 years.