One of the most important factors in the declining share of Christians and the growth of the “nones” is generational replacement. As the Millennial generation enters adulthood, its members display much lower levels of religious affiliation, including less connection with Christian churches, than older generations. Fully 36% of young Millennials (those between the ages of 18 and 24) are religiously unaffiliated, as are 34% of older Millennials (ages 25-33). And fewer than six-in-ten Millennials identify with any branch of Christianity, compared with seven-in-ten or more among older generations, including Baby Boomers and Gen-Xers. Just 16% of Millennials are Catholic, and only 11% identify with mainline Protestantism. Roughly one-in-five are evangelical Protestants.
In many disciplines, Western methods of conducting research are predominant.  Researchers are overwhelmingly taught Western methods of data collection and study. The increasing participation of indigenous peoples as researchers has brought increased attention to the lacuna in culturally-sensitive methods of data collection. Non-Western methods of data collection may not be the most accurate or relevant for research on non-Western societies. For example, " Hua Oranga " was created as a criterion for psychological evaluation in Māori populations, and is based on dimensions of mental health important to the Māori people – "taha wairua (the spiritual dimension), taha hinengaro (the mental dimension), taha tinana (the physical dimension), and taha whanau (the family dimension)".