Bilateral asymmetry in pedaling is well-known and long-studied. You can see the abstract of a review of what is known about bilateral asymmetry in running and cycling here. During cycling, bilateral pedaling asymmetry is common, and not fixed at a particular split: it varies with cadence, power, duration, and your ride goals. Another article that is highly cited is Smak et al. (1999), which found that bilateral asymmetry varies with cadence. The asymmetry appeared to decrease within increasing cadence, though the power was held constant so it could as easily have been a story about crank torque.
In summary bilateral asymmetry appears to vary for each individual depending on his or her cadence, power, crank torque, and level of fatigue. This appears to be normal. It is unclear that one can easily alter one's pedaling symmetry or asymmetry, nor is it clear in cycling that small amounts of pedaling asymmetry lead to injury (since the asymmetry is so common).
As an aside, non-constant asymmetry has the potential to affect measurements from "single-sided" power meters.