Funnily enough, there was a *Science* article published on this ([see here][1]).

In their sample of university students, Mehl et al. report (emphasis mine):

>The data suggest that women spoke on average 16,215 (SD = 7301) words and men 15,669 (SD = 8633) words over an assumed period of, on average, 17 waking hours. Expressed in a common effect-size metric (Cohen’s d = 0.07), this sex difference in daily word use (546 words) is equal to only 7% of the standardized variability among women and men. Further, the difference does not meet conventional thresholds for statistical significance (P = 0.248, one-sided test). **Thus, the data fail to reveal a reliable sex difference in daily word use. Women and men both use on average about 16,000 words per day, with very large individual differences around this mean.**

Although, it's possible that we might see systematic differences depending on factors other than sex (e.g., SES, age).


  [1]: http://www.psicol.unam.mx/profesionales/PsiClinica/iem/MehlScience2007.pdf

### References
* Mehl, M. R., Vazire, S., Ramírez-Esparza, N., Slatcher, R. B., & Pennebaker, J. W. (2007). Are women really more talkative than men?. Science, 317(5834), 82-82.