Does your old iPhone seem slower now that Apple has released the iPhone 6S?
You're not alone. As this chart from Statista shows, every time Apple comes out with a new iPhone, search queries for the term "iPhone slow" peak right around launch time, then decline slowly after that....until the next release.
Part of it might just be jealousy when you see your friend surfing the web at lightning speed thanks to the newest processors and software. But there's also some evidence that new versions of iOS slow older iPhones down, as new features take up more processing power, so people may simply be regretting their latest software upgrade.
See the evolution of the iPhone in photos: