Thus, the question to be asked is whether the tax is imposed "on all transactions of the relevant kind without differentiation based on the source or destination of the goods", and if the tax refers to a particular market, the material factor is the effect of the tax on transactions in that particular market.
The question at hand seeks to determine whether the tax is applied equally to all transactions of a certain nature, irrespective of their origin or final destination, and if it pertains to a specific market, what matters most is how the tax affects transactions within that particular market.