Seniors are by far the fastest growing market segment in the United States. It’s also one of the most lucrative. According to the latest U.S. census, this demographic comprises 37 percent of the total U.S. population and will grow to 45 percent this year. Seniors also possess approximately $1.6 trillion of all the disposable income in the country and have a combined household net worth of around $19 trillion. They also spend a cool $7 billion online each year.