for example there might be some theory somewhere that the way to measure the growth of the economy is to take something relatively unchanged since ancient times, like a chicken and then calculate the amount of biomass change taken up by chickens since that time (this is a spur of the moment wrong idea here) but some animals have increased in biomass and then decreased because the demand for them has not continuously risen over time - for example: horses. If one used the biomass idea then it would see the economy increased steadily from ancient times to near modern and then there was a startling depression that wiped out several hundred years of economic progress.

Of course nobody is doing this silly thing, but trying to think about how the way it is being done works seems to be equally as silly to me.