And these electric scooters aren't as environmentally friendly as you'd hope. Scientists at North Carolina University have shown that they carry carbon footprints as big as conventional cars and 3.5 times the size of electric vehicles. Even so, this partial solution has been lucrative for some investors — Chinese scooter company Niu Technologies' stock jumped as much as 500% within the span of few months, though shares have since come back down to Earth. Even traditional car companies like Ford Motor Co. F that are staking claims to the scooter-sharing business have risen in recent months.