What is the scientific effectiveness of "street preaching" as a method of evangelization?

I've been looking around for hard facts on the efficacy of street preaching but can't find any. Are there any hard numbers on the number of people who come to faith through this kind of evangelism? Has its efficacy changed over time? In Acts 2 Peter seems to use the same kind of technique with quite some effect. In my experience street preachers seem to be mostly met with either indifference or derision however that is entirely anecdotal. So, scientifically, how effective is street preaching as a method evangelism? --- Since I know of no studies I cannot define exactly what "efficacy" and other terms are in this instance, but I leave that to any studies if they exist.