Communication.We divided the world’s tech-nological communication capacity into twobroad groups: One includes technological sys-tems that provide only unidirectional downstreamcapacity to diffuse information (referred to asbroadcasting), and one provides bidirectional up-stream and downstream channels (telecommu-nication). The ongoing technological convergencebetween broadcasting and telecommunicationis blurring this distinction, as exemplified by thecase of digital television, which we counted asbroadcasting even though it incorporates a smallbut existent upstream channel (such as video-on-demand).Fig. 4.World’s technological effective capacity to telecommunicate information (table SA2) (16).Fig. 5.World’s technological installed capacity to compute information on general-purpose computers,in MIPS (table SA3) (16).1 APRIL 2011VOL 332SCIENCE62RESEARCH ARTICLES
The inventories of Figs. 3 and 4 account foronly those bits that are actually communicated. Inthe case of telecommunication, the sum of theeffective usages of all users is quite similar to thetotal installed capacity (any difference representsan over- or future investment). This is becausemost backbone networks are shared and onlyused sporadically by an individual user. If allusers demanded their promised bandwidth simul-taneously, the network would collapse. This isnot the case for individual broadcast subscribers,who could continuously receive incoming infor-mation. To meaningfully compare the carryingcapacities of each, we applied effective consump-tion rates to the installed capacity of broadcasting(calling it the effective capacity). This reducedthe installed capacity by a stable factor (by 9 in1986, 9.1 in 1993, 8.7 in 2000, and 8.4 in 2007),implying an average individual broadcast con-sumption of roughly 2 hours and 45 min per 24hours. It did not notably change the relativedistribution of the diverse technologies (Fig. 3).Figure 3 displays the capacity of six analogand five digital broadcast technologies, includingnewspapers and personal navigation devices [glob-al postioning system (GPS)]. In 1986, the world’stechnological receivers picked up around 432exabytes of optimally compressed information,715 optimally compressed exabytes in 1993, 1.2optimally compressed zettabytes in 2000, and 1.9optimally compressed zettabytes in 2007. Cableand satellite TV steadily gained importance, butanalog,“over-the-air”terrestrial television stilldominated the evolutionary trajectory. Digitalsatellite television led the pack into the digitalage, receiving 50% of all digital broadcast signalsin 2007. Only a quarter of all broadcasting in-formation was in digital format in 2007. The shareof radio declined gradually from 7.2% in 1986to 2.2% in 2007.Figure 4 presents effective capacity of thethree most common bidirectional analog tele-communication technologies and their four mostprominent digital heirs. The 281 petabytes of op-timally compressed information from 1986 wereoverwhelmingly dominated by fixed line teleph-ony, whereas postal letters contributed only 0.34%.
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Test, Data storage device, Computer data storage, Digital television, Exabytes