What is the annual global consumption of laundry detergent?

This inquiry exemplifies a Fermi problem, which involves making rough estimates with minimal or no actual data. The question pertains to the total global consumption of laundry detergent each year. Interviewers typically pose such questions to evaluate your logical reasoning, problem-solving skills, ability to make assumptions, and your capacity to perform calculations swiftly and accurately. Your response should rely on sensible assumptions, detailing each step of your calculations. Aim to simplify wherever possible and refrain from using overly complex methods. Clearly express the assumptions you are making and the rationale behind them. To effectively respond to this question: Estimate the global population. Estimate the proportion of individuals who use laundry detergent. Estimate how often it is used and the quantity of detergent utilized per use. Multiply all these values together.

Considering the global population is approximately 7.8 billion individuals, I will further analyze the percentage of people likely to be regular laundry detergent users. It is estimated that around 60% of this population consists of families with consistent access to washing machines, which amounts to roughly 4.68 billion people. If we assume an average family size of four, this translates to about 1.17 billion families utilizing laundry detergent worldwide. If these families wash their clothes twice a week and use around 100 milliliters of detergent per wash, that results in 200 milliliters of detergent each week. Over the course of a year, this totals 200 milliliters multiplied by 52 weeks, equating to approximately 10.4 liters of detergent consumed by each family annually. Consequently, when we multiply 1.17 billion families by 10.4 liters, we arrive at an estimated total of around 12.2 billion liters of laundry detergent used globally each year.

To begin, I will estimate the global population to be around 7.8 billion. Out of this number, I believe that around 70% have regular access to washing facilities and utilize laundry detergent, which amounts to approximately 5.46 billion individuals. If we assume that the average person does laundry once a week and uses about 75 milliliters of detergent each time, that translates to 75 milliliters per week. Therefore, over the course of a year, each person would use 75 milliliters multiplied by 52 weeks, which is roughly 3.9 liters. As a result, if we multiply 5.46 billion people by the 3.9 liters of detergent consumed per person annually, we arrive at an estimated total of 21.3 billion liters of laundry detergent used worldwide each year.