In the book, Slavery, Terrorism and Islam: The Historical Roots and Contemporary Threat, written by Dr. Peter Hammond, he explores the topic of the impact that an increasing Muslim population has on that society. The lists below illustrate theMuslim population status of countries around the world, and exactly what changes to the societies can be expected according to Hammond.
The book as well as the author are controversial, but the topic is definitely something that needs to be explored and understood. From the book:
As long as the Muslim population remains around or under 2% in any given country, they will be for the most part be regarded as a peace-loving minority, and not as a threat to other citizens. This is the case in:
United States -- Muslim 0.6%
Australia -- Muslim 1.5%
Canada -- Muslim 1.9%
China -- Muslim 1.8%
Italy -- Muslim 1.5%
Norway -- Muslim 1.8%
At 2% to 5%, they begin to proselytize from other ethnic minorities and disaffected groups, often with major recruiting from the jails and among street gangs.
Full text at: http://www.examiner.com/article/as-muslim-population-grows-what-can-happen-to-a-society