Notice also the strong inter-annual variation, which is normal and independent of machine performance.

Offshore wind technology is moving completely away from the standard technology represented by these statistics.

"Life shrinks or expands in proportion to one's courage." - Anaïs Nin

newer wind farms performed well and continue to do so; older ones performed more poorly and still do. Ergo: performance diminishes with age... hmm, isn't this what they call the 'ecological fallacy'? The confounder being the year of construction.

Makes a lot of sense...thanks.

Wind power

What you have pointed at is standard when a new technology is introduced into the market.  The IBM 1401 solid state computer was a huge hit in the market, solving a number of major business problems, when it was introduced in 1959.  Five years later IBM introduced the System/360 a technically superior product to the 1401, yet the 1401 continued to sell until it was withdrawn in 1971.  Even after IBM no longer sold the 1401 the machines continued to adequately accomplish business tasks; I worked on a 1401 in 1976 (IIRC) programming new business tasks and extending functionality of existing programs.

Let me list a couple of things:

1.  People invest in technology when the existing functionality meets their needs (or financial forecasting, financial ratios, cash flow analysis, & etc.) at a specific point in time.  

2.  The GO/NO-GO decision to purchase technology at a point in time is made with the knowledge at that time.  (Like, duh.)  

3.  It is doubtful the "superior" IBM System/360 would have been built if the "inferior" 1401 had failed in the market.

4.  It doesn't matter if a "superior" machine is available latter when the "inferior" machine is meeting the needs, tasks, goals, financial return, etc. assigned at the time of the GO decision.

5.  Both users and producers of technology climb a learning curve.  The users learn how to use the stuff better, the producers learn how to make the stuff better, and (ideally) they interact in a virtuous positive feedback to the benefit of both.

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre