From this paper:
Data points indicate best performers by year of market introduction.
The magnified plot shows progress in cool white LEDs from 1996 to 2020. For comparison, efficacies of best performers in legacy lighting technologies for 2020 are shown as coloured horizontal lines.
Note the logarithmic scale of the vertical axis on the main plot and the linear scale on the magnified plot.
From this article:
most improvements in the energy efficiency of LEDs were driven by research and development efforts. Surprisingly, however, R&D contributed relatively little to reductions in the cost of the devices, which were instead linked to economies of scale and continuous manufacturing process improvements over time.
