In 1971, 1 percent of U.S. citizens described themselves as vegetarians. In 2008 Harris Interactive found that 3.2% are vegetarian and 0.5% vegan. U.S. vegetarian food sales (dairy replacements such as soy milk and meat replacements such as textured vegetable protein) doubled between 1998 and 2003, reaching $1.6 billion in 2003. In 2015, a Harris Poll National Survey of 2,017 adults aged 18 and over found that eight million Americans, or 3.4%, ate a solely vegetarian diet, and that one million, or 0.4%, ate a strictly vegan diet. A 2018 Gallup poll estimated that 5% of U.S. adults consider themselves to be vegetarians. Older Americans were less likely to be vegetarian with just 2% of adults aged 55 and older saying they follow a vegetarian diet. Younger generations of Americans are more likely to be vegetarian with 7% of 35- to 54-year-olds and 8% of 18- to 34-year-olds following a vegetarian diet.