*Reference: the EIA, using databrowser with query similar to <a rel="nofollow" class="external autonumber" href="http://www.eia.gov/cfapps/ipdbproject/iedindex3.cfm?tid=2&amp;pid=2&amp;aid=12&amp;cid=all,&amp;syid=1980&amp;eyid=2011&amp;unit=BKWH">[1]</a>
<ul><li>Graph created in Gnumeric.</li></ul>
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