A Single core performance has improved by an average of 30% per year for the last five years.
Back the late nineties the rate of increase in cpu horsepower was phenomenal, every two years processor throughput was doubling. As clock speeds reached 3 and then 4 GHz the emphasis shifted from linear single processor speed to multi-threaded performance. There has been a relatively slow and predictable improvement in performance over the last five years and there is no longer the need to upgrade a CPU more than once every three years. In terms of single core performance, a reasonable proxy for real world performance, the late 2007 Core2 Duo E6550 scored 881 points on PassMark-S vs 2080 points achieved by the Mid 2012 Core i7 3770K, roughly a 140% increase in performance over the last five years or roughly a thirty percent improvement per year.

The Best.
CPUGPUSSD
AMD Ryzen 5 1600 $175Nvidia GTX 1070 $447Samsung 850 Evo 250GB $104
Intel Core i7-8700K $320Nvidia GTX 1060-6GB $270Samsung 850 Evo 500GB $117
Intel Core i5-8600K $239AMD RX 480 $280Samsung 850 Pro 256GB $116
HDDRAMUSB
Seagate Barracuda 1TB (2016) $45Corsair Vengeance LPX DDR4 3000 C15 2x8GB $177SanDisk Extreme 64GB $44
Seagate Barracuda 3TB (2016) $80G.SKILL Trident Z DDR4 3200 C14 4x16GB $911SanDisk Extreme 32GB $30
Seagate Barracuda 2TB (2016) $58HyperX Fury DDR4 2133 C14 2x8GB $226SanDisk Ultra Fit 32GB $12
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