Computer storage, primary and secondary memory, has seen a tremendous phase of development over the last fifty years. As new technology has been brought to the market prices have continued to decline steadily at a logarithmic scale. For magnetic storage, the trend has been very stable over the last thirty years, with prices per MB going down around a third every year, or a ninety percent every five years. For primary storage, the trend has been more volatile, but overall we see a similar rate of decline all the way back to the first flip-flops in the 1950s.
John C. McCallum has done a good job collecting all the data over the years, and going back to computer magazines for reference. However, since the beginning of 2012 there have been no updates, so I’ve taken up the work where he left off. All data prior to March 2012 is collected by McCallum, while data after January 2013 is partly added by myself (source marked in new data files linked below). For his original data sets, see his web site [magnetic, memory, flash].
Following McCallum’s example, I’ve continue use the “lowest priced [items] for which I could find prices at the time”. Over the last years, the main source has been the USD price at NewEgg.com. There, prices are generally stated free of shipping charges, but sometimes with “rebates”, which is probably more marketing than a special reduction in price. A new price point is added every one or two months.
For RAM, capacity is counted in MiB (1024 * 1024 bytes, base 2), since that still reflects the nature of that medium. However, for harddisks (spinning and solid state) now up in multiple tera bytes this no longer makes sense. Harddisk platter density is not measured in MiB, but rather MB (1000 * 1000 bytes, base 10), and is also sold by that unit; thus a 3 TB harddisk can be expected to store 3×1012 bytes, rather than 3×240 = 3.3×1012 bytes. Of course, when calculating cost per MB, base 10 is always used. The raw data files make this clear.
Raw data and Gnuplot script
If you would like to investigate the details of the data, or reconstruct the graph, the raw data files and Gnuplot script are available here.
McCallum’s original copyright notice was simply “You can use the contents here. Please acknowledge the source”.
I’ve used the Creative Commons License with the Attribution and ShareAlike sections, in the hope that the data and chart will continue to exist in open form. Thus, the data, Gnuplot script and chart are licensed under the Creative Commons Attribution-ShareAlike 3.0 Unported License.