Almost, but not quite. Demand is, to a significant extent, income-based. There are two types of demand: Essentially fixed demand (which varies only slightly based on income), and then there is discretionary demand.
They are easily identified. Non-discretionary spending is comparable to parents buying food, clothing, etc for the family. This is a fairly consistent amount every month/year and is spent on a range of goods and services that is fairly uniform year after year. Discretionary spending is the money given to their teenage kids to spend on whatever they want. This amount changes every month and is not in any one category unless it might be called the “what I want NOW” category. Clothing one month, music another month, Taylor Swift concert another month, and so on.
Thus, the inputs for demand for each general/specific category will average out over a period of time–but may also be highly cyclical (i.e. Christmas, St Patrick’s day stuff, and so on). The inputs will vary significantly based on expected demand for discretionary spending while demand for non-discretionary spending does not change much, so those inputs do not really change over time. It is also why companies (and school districts) are aware of population trends. More/fewer babies means more/fewer diapers, need for school TYPES (i.e. pre-, elementary, middle, high schools over time). And lots more.