The Company’s stock crashes after financial analytics firm Selerity posts a quarterly report before the stock market closes. The report shows revenue growth at 74 percent in the quarter, which is below the company’s own forecasts. Twitter shares plunge on the news, and trading briefly halts so the company can disseminate its results. The drop steepens and the stock ends the day down about 18 percent. Executives attribute the slowdown to a transition to an advertising model that prices certain ads based on the result, such as whether the viewer downloaded an app, instead of whether the person simply clicks on it.