Slow draining bathroom sink
To bring the issue to a conclusion I ended up bringing in a plumber.  It took him about ten minutes with a powered auger to locate the partial blockage in the pipe.  The blockage was located about 12 feet into the pipe.  It was an expensive resolution for 10 minutes work but at least the issue has been resolved.  I will perhaps purchase a better auger so as to deal with future issues.  Thanks to all that gave suggestions on how to deal with the issue.