The conventional start of the photovoltaic module price series

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The year from which the standard long-run module price series is usually drawn, at a price of the order of a hundred United States dollars per watt in the money of the day. It is a convention of the data rather than an event in the technology: 1976 is simply where a continuous, comparable price record begins. It matters because it fixes the baseline against which the roughly three-order-of-magnitude decline is measured, and because that baseline is what makes the decline legible as a learning curve rather than as a series of unrelated improvements.

A node is not a place. Drawing it on a map would assert something about the world that no stored fact supports.