This article deals with the changes to the demographics of Israeli settlement in the West Bank and East Jerusalem from 1967 to 2013. It reviews the demographic data on the Jewish settler population, population growth, net migration, and ethnic distribution, and discusses the direct and indirect factors influencing the increase in settler numbers and in migration to the settlements. It also presents forecasts for the growth in the settler population until 2048. The article asserts that the rise in the number of settlers is a result of two factors: migration to the settlements and very high natural population growth among the settlers. The first factor can be explained by policies that promote migration to settlements and provide economic conditions and social services to support migration. The second (very high natural growth) can be explained by the nature of the settlers and their levels of religiosity and right-wing/nationalist ideology. The article clarifies that the relative importance of these two factors has varied according to the various political stages. In the early settlement period, migration was the main factor accounting for increasing numbers of settlers, while the high birth rate accounts for the increase in settler numbers witnessed over the last 20 years in the West Bank, but not in Jerusalem.