Figures \ref{873958} and \ref{885954} present the evolution of capacity weighted mean wind speeds for onshore of onshore and off-shore wind turbine projects in selected countries across the world. One can clearly observe the exponential decay of the mean wind speeds over time. We note that two phenomena are simultaneously occurring influencing the trends:
We can see that in the onshore case, all countries (even China) follow a very similar decay pattern, and even a similar decay rate, the only outlier is the United States, and that is mostly due to its territorial differences in geography and the differential start of different regions. Examining the US data regionally, it becomes apparent that the intra-state patterns are the same for the states with large wind turbine deployment, such as Iowa, Oklahoma, California and Texas.