Right side. The reasons given above are why.

In my youth I went thru a period where I rode a 1 mile section salmoning. This lasted about 6 months. During this period I noticed the incidence of near misses were several times higher than while riding the right side. I don't think there was even one of these rides without at least 2 near misses.

It was easy to see that car drivers turning right onto the street would glance once to the right. Not see me or discount me as a pedestrian too far away. Then watch intently to the left. Once it was clear to their left they would take off without looking again to the right. People turning left off the major street aren't even looking for you at all.

Finally I was clipped. After that I quit salmoning. Well 99% of the time. I will still do it for a very short distance but am very aware of the dangers when doing so. Say for instance I want to go to a store on my left on the left side of the road 2 doors down. That is still a cause of near misses. Even going slow.