 Although farmers expressed concern at the damage caused to their crops, local response to the appearance of crop circles was often enthusiastic, with locals taking advantage of the increase of tourism and visits from scientists, crop circle researchers, and individuals seeking spiritual experiences.The market for crop-circle interest consequently generated bus or helicopter tours of circle sites, walking tours, T-shirts, and book sales.Since the start of the 21st century, crop formations have increased in size and complexity, with some featuring as many as 2,000 different shapes and some incorporating complex mathematical and scientific characteristics.