The term "national average" refers to an aggregate measure or statistic that represents the general trend, behavior, or characteristic of a particular population, group, or phenomenon across an entire country. It is calculated by taking into account various data points and statistics from different regions, demographics, and sources, and then combining them in such a way as to provide an overall picture of what is typical, normal, or expected for that particular characteristic or behavior within the population being considered. In other words, it represents the middle value or central tendency of the data, and can be used as a benchmark or standard against which individual observations, values, or behaviors can be compared to determine how they deviate from or conform to the norm.