I’ve not read the Rifkin book, so it may have a response to the criticism I’m about to make of your rendition of the key idea.
“The margin” is a concept that is set in a temporal context. That is, the margin is about a decision being made. Historically, economists think primarily of the short term margin: changed to production that can occur without changes in capital (and so, prototypically only using variations in inputs such as labor, energy, and raw materials). This is where marginal cost can fall to zero.
But economists also recognize two further changes, which can be classified as medium and long term margins, but which is which often depends on the structure of the industry. One type of change is the application of additional capital. Typically, this is the medium term margin. The second is competitors entering or exiting the market. This is usually the long-term margin. At this margin, marginal costs never ever fall to zero.
Under a condition of zero short-term marginal costs driving prices below the long-term average cost, competitors will exit the market or differentiate themselves. In the former situation, you eventually arrive at a duopoly or monopoly. In the latter situation, you end up with monopolistic competition (which I think is a fairer description of most consumer goods, for example).
Thus, I think the idea of prices generally falling to zero because short-term marginal costs fall to zero is misplaced. To put it simply, marginal costs are not total costs.
I’ve not read the Rifkin book, so it may have a response to the criticism I’m about to make of your rendition of the key idea.
“The margin” is a concept that is set in a temporal context. That is, the margin is about a decision being made. Historically, economists think primarily of the short term margin: changed to production that can occur without changes in capital (and so, prototypically only using variations in inputs such as labor, energy, and raw materials). This is where marginal cost can fall to zero.
But economists also recognize two further changes, which can be classified as medium and long term margins, but which is which often depends on the structure of the industry. One type of change is the application of additional capital. Typically, this is the medium term margin. The second is competitors entering or exiting the market. This is usually the long-term margin. At this margin, marginal costs never ever fall to zero.
Under a condition of zero short-term marginal costs driving prices below the long-term average cost, competitors will exit the market or differentiate themselves. In the former situation, you eventually arrive at a duopoly or monopoly. In the latter situation, you end up with monopolistic competition (which I think is a fairer description of most consumer goods, for example).
Thus, I think the idea of prices generally falling to zero because short-term marginal costs fall to zero is misplaced. To put it simply, marginal costs are not total costs.