This subject is very interesting, as big part of speech pathologists believe that stuttering rate is the same everywhere, and only a minor part believe that there are substantial differences in the rate of stuttering in different populations. Those who believe the rate is same everywhere, unfortunately, are not interested in cross-cultural studies. After asking people from different cultural background for many years about stuttering, I found that the differences in the incidence are absolutely huge. For example, you will find that a huge number of people from sub-Saharan populations had a stuttering problems (many have it as adults as well). On the other hand, you can hardly find a stuttering individual among the Chinese, or among Native Americans. Unfortunately, most of the "serious" speech pathologists are not interested to examine these cultural differences, instead they try to explain the published data on the existing differences by different methodologies used by different speech pathologists in different populations. But how come that experts, almost educated in Western Universities, always make the same "mistakes": they exaggerate the number of stutterers in sub-Saharan Africa (and African Americans), and grossly underestimate the number of stutterers among American Indians and Chinese populations. Fearing to face facts has never helped anyone in finding the real causes of any phenomena. I very much hope that many professional speech pathologists will read this blog and comment from their own experience on this topic.In the past, I wrote that stuttering is relatively constant across cultures. I am not so sure any more. For following reasons:
(a) Stuttering is driven by genetic mutations. Different ethnic groups have different mutations in their gene pool. So some could have more or less of these mutations.
(b) Stuttering might not occur due to certain genes, which again might differ in different gene pools.
I am not surprised that a difference between Sub-Saharan and other groups exists. The latest research on Neanderthal DNA has shown that Sub-Saharan groups do not have any Neanderthal genes. Only those groups getting out of Africa have Neanderthal genes. Moreover, those groups were very likely under severe evolutionary pressures to adapt to different habitats. Speech might have been a critical feature, and mutations have been selected out.
I haven't looked yet at empirical studies, but I would be surprised if such research exists and is water tight.
I revise my statement:
(a) Stuttering exists in all cultures.
(b) Prevalence might vary.
Here is also an older post on the topic.