There is no non theoretical way to measure demand and supply separately from market data. All prices, for example, already include not only costs, but expectati

There is no non theoretical way to measure demand and supply separately from market data. All prices, for example, already include not only costs, but expectations of demand. You need data that includes so called demand shifters or demand multipliers, to estimate the supply and vice versa. That is, if you observe a supply independent shift of demand, you can use that measure of to identify supply parameters. Even if you di this non parametrically, you implicitly impose a model. Supply and demand is one of the origin problems of the theory of statistical identification and causal analysis.