Identify the woman's voice in literature?
Your question is not quite clear.
Do you wish to know how women are represented (their characterization) in literature, or how female authors represent a feminine point of view, or whether the number of female authors are representative enough to have a voice and if so, do they represent or deal with issues unique to women - do they stand up for women?
If you've answered 'yes' to the first part of the question, then one needs to explore how women have been characterised throughout literate history. One has to delve into the history of writing from the earliest manuscripts to current writing.
Obviously, the manner in which women were, and are presented, will match the norms, standards, cultures and beliefs of the period in which the writing was done. What is also important then, is the geography (setting) during the period, since different ideologies were, and are, applicable during different periods and the writing would reflect this discrepancy.
If your answered in the affirmative to the second part of the question, it should be clear that female authors would more than likely offer an alternative perspective and opinion regarding events and experiences to that of a male writer. In this sense then, the author would be representative of the "woman's voice."
This, however, is not to say that male authors did or do not provide a voice for women in their writing, or that female author's strictly only represent a "woman's voice", since numerous male and female authors represented both a male and feminist perspective in their works, irrespective of their own gender.
If your answer was 'yes' to the third part of the question, then yes, women have played a significant role in literature to be deemed as having a "voice." We have had many female authors (too numerous to mention for this response) who have achieved much and have succeeded in their craft - winning major awards and enthralling the world with their invigorating and intelligent writing.
One can mention the Bronte sisters, Anna Sewell, Mary Shelley, Harper Lee, Maya Angelou, Olive Schreiner, Jane Austen, Irma Bombeck and many, many others who have been, and will be, "the woman's voice in literature" for time immemorial.