Majority of studies and measurements show that remote working leads to happier, less stressed workers spending more time on task. Previous studies have shown those are key factors in driving productivity.

The notable difference is that manager reported productivity often show worse measures as unchanged or lower productivity, even where less subjective measures show increases.

Some studies have tried to measure productivity directly, these commonly have unaddressed problems with methodology, and show more mixed results ranging from slightly less productive to significantly more productive.

I seem to remember a study measuring rate of completion of task lists as much more productive, including call centers, IT, customer service and sales. Whereas more nebulous tasks in management and group facilitation suffered slightly.

I'm thinking it's due time for a meta study on the topic though, maybe you could put one together?