If the west's population is top-heavy, (i.e., the ratio of youth to elderly is low) that of Muslim populations is the opposite. For example, today more than half the population of Algeria is under the age of twenty and this situation is similar elsewhere. These young populations will reproduce and perpetuate the increase of Muslims on a percentage basis well into the next millennium.
North America and Europe have increasingly aging populations and one of the most disturbing social issues of the new millennium will concern a more efficient means of disposing of the elderly. (For example, witness the new euthanasia laws in the Netherlands, and the ongoing debate in many countries about this issue.) Medical advances can assure an average life span in the high seventies, although active life spans have not grown as fast. In the early 1900s, a westerner could expect to spend an average of the last two years of life as an invalid. Today, that figure is seven years. As Ivan Illich has shown, medicine prolongs life, but can not prolong mobility nearly as well. Aging populations with their increased healthcare costs are considered a more extensive socio-economic burden to society. For example, the UK Department of Health recently announced that a new prescription drug for Alzheimer's Disease was available on the National Health Service - but its cost meant that it was only available to a small minority of patients.
