aspects of their birth culture (the first culture) and the new culture (the second culture), creating a unique "third culture". Globally, offspring of military households comprise about 30% of all TCKs, but they are almost exclusively from the United States. Start of Department of Defense research Systematic research on individuals in such environments has been conducted since the 1980s. Responding to social and psychological issues recorded in military families and communities, the U.S. Armed Forces sponsored research on the long-term impact of growing up as a military dependent. Outside of the U.S. there is no significant literature on the effects of growing up as a military dependent. Since the Department of Defense does not track or monitor former brats, any study on adult brats is based upon self-identification. Thus, even though the studies are performed using scientific sampling methods, they may contain bias because of the difficulty in conducting epidemiological studies across broad-based population samples. Some researchers used referrals, the Internet, and newspaper articles to identify military brats. Mary Edwards Wertsch: Identification of military brat cultural identity In 1991, Mary Edwards Wertsch "launched the movement for military brat cultural identity" with her book Military Brats: Legacies of Childhood inside the Fortress. In researching her book, Wertsch identified common themes from interviews of over 80 offspring of military households. While this book does not purport to be a scientific study, subsequent research has validated many of her findings. In the introduction to the book, former military brat Pat Conroy, the author of The Prince of Tides and The Great Santini, wrote, Brats: Our Journey Home In 2005 military brat and filmmaker Donna Musil released the first documentary ever made exclusively about military brats, Brats: Our Journey Home. To date, the documentary has won six film awards. Musil furthers the premise that military brats form a distinct American subculture with a commonly held sense of identity that is actually a distinct American ethnicity. The documentary also draws on many studies interviews of researchers, counselors and psychologists, along with interviews of numerous former military brats. Perceived invisibility of culture and experiences Musil's documentary also highlights the feeling among many military brats that the culture and lives of military brats are largely invisible to most Americans. Some sparse and superficial aspects of military brat life may be known, but a fuller sense of awareness of one of America's largest (and oldest) subcultures is largely