Thanks for your answer. Do you have a bibliographic reference for Wilde's work?  

I am interested in numbers which reflect those people who would benefit from materials published in a sign language.  There are no good censuses that I have found.  These often include people who are elderly and have recently become deaf.

I have visited many countries and worked with Deaf people in those countries.  One of the things I ask them is whether they were born deaf or whether they became deaf later in life.  In the economically poorer countries the vast majority of the Deaf became deaf as children.  I have noticed that this percentage tends to drop in those countries which are more developed economically.

Recently I was researching Deaf Bhutanese refugees resettled in Western countries.  I had received a request for help from a charity in the US.  People were amazed at the percentage of Deaf people among the refugees.  I found a survey of a refugee camp in Nepal which looked to be a fairly good census and which surveyed the whole population.  The percentage they found was within the range I expected.  So, this very small sample was a partial validation :-)

In my  opinion, not physically but mentally deaf population rate should be examined in order to find a negative causal path to human development level :) 

Unfortunately, formal data in our country also presents not directly the deaf (who are users of sign language and lives in a habitat centralized at/around sign language) but all with hearing problems in any ages. 

I published a few studies to find out the data of real "deaf " population in Turkey for a few years in Turkish. Only one which is also available in ResearchGate (The history of sign language and deaf education in Turkey) is in English. But this paper is mostly related with problems of the deaf in Turkey and also their history in and around Anatolia. None of development indices, but their current problems in education (schooling, special education, university education, etc) were mentioned.

We (me and Pinar Yaprak Kemaloglu) have some other works which are already presented as only conference papers about "social institutions"  (available in ResearchGate: An Investigation of the Social Institutions Regarding Deaf Citizens in Turkiye), and "sports". And some data about problems and proposals in higher education settings for the deaf young which was taken from "E-işit" project, (supported by the Worldbank a few years ago) is also present in ResearchGate as a conference paper. Currently I published another paper about the necessity of sign language in medical services (Dysability, Otorhinolaryngologic Practice and Sign Language) which is also Turkish.

Recently a book is prepared by some researchers in Turkey (but not published yet; editor: E Arik), which is about sign language researches in Turkey, and in this book not only me but also some other researchers pointed out many aspects of Turkish deaf society.

Now I am about to set a research on medical problems and health status of the deaf, which will be done in sign language through the deaf societies in Turkey.