My Passport slow transfer rate

A couple of weeks ago my My Passport 500 gb external was running fine with a good transfer rate but all of a sudden when I reconnected my external to my mac, the transfer rate is slower than usual. My connections are USB 2.0 but why is my transfer rate slow?

Make sure you’re using the short usb cable that came with it, even if your computer has usb 2.0, that can be lack of power therefore the drive is not performing well… Or try to use a power booster cable " y shape cable"… If still acting slow, format the drive and try it again, if still slow, replace it.