Publicly traded solar companies are having no better time on Wall Street than banks or traditional industries. Today one thin-film solar company saw its shares drop over 20%. Just slightly above its 52-week low set in November. Solar companies are seeing a slowdown in purchases in 2009, and longer periods between billing and actual payment. A sinking economy lowers all boats. One study of the solar sector predicts as much as $7 billion will fall off the annual revenue of solar conmpanies worldwide this year. 2008 saw estimated revenues of $36 billion US.