(San Francisco, CA)  --  Twitter's growth will slow in the coming years.  A new long-term forecast from eMarketer predicts that Twitter's global user base will increase over the next five years, but with diminishing returns. 

Growth this year is pegged at nearly 25 percent.  By 2018, eMarketer predicts Twitter's growth at less than eleven percent.  Last Friday, the company's stock hit its lowest closing price since its IPO in November.