Financial gerontology is a multidisciplinary field of study encompassing both academic and professional education, that integrates research on aging and human development with the concerns of finance and business. Following from its roots in social gerontology, Financial gerontology is not simply the study of old people but emphasizes the multiple processes of aging. In particular, research and teaching in financial gerontology draws upon four kinds of aging or "'four lenses" through which aging and finance can be viewed: population aging, individual aging, family aging, and generational aging. While it is problematic that "demography is destiny," demographic concepts, issues, and data play a substantial role in understanding the dynamics of financial gerontology. For example, through the lens of population aging, demography identifies the number of persons of different ages in cities and countries—and at multiple points in time. Through the lens of individual aging, demography also notes changes in the length of time—number of years lived in older age, typically measured by increases in life expectancy. From in its founding years in the beginning of the 21st century, one primary interest of Financial Gerontology has been on baby boomers and their relationships with their parents. The impact of these two kinds of aging on finance are reasonably apparent. The large and increasing number of older persons [population aging] in a society, no matter how "old age" is defined, and the longer each of these persons lives [individual aging], the greater the impact on a society's pattern of retirement, public and private pension systems, health, health care, and the personal and societal financing of health care. The focus on boomers illustrates also the other two lenses or "kinds" of aging. How boomers deal with the social, emotional, and financial aspects of their parents' aging is a central aspect of family aging. And how boomers may differ from their parents born and raised twenty to forty years earlier, and differ from their Generation X and Millennial children and grandchildren, are substantial aspects of generational aging.