Pickleball grew nearly $40\%$ in the United States between $2019$ and $2021.$ This sport once played primarily by the over $55$ crowd, was the rage with a much younger demographic. Many manufacturers cranked up production of pickleball equipment and many gyms, country clubs and other sporting venues added pickleball courts. As the younger demographic returns to tennis and other pre$-$COVID sports, pickleball equipment fills the shelves through Dick's and many other retailers distribution channels and many courts sit idle. The rise and fall of pickleball is an example of $\_\_\_\_\_.$