The software needed to make the animation has developed rapidly. My first attempt to visualize the trade network in January 2015, using Gephi, looked like this:
The first animation appeared in March 2015 as an animated GIF:
By April 2015 we had a second animation made using Sonoma that is a movie (mp4) and presents the full set of years:
The new animation, completed in October 2017, is a major step forward both in the number of observations and the attractiveness of the geographic projection. I thank the makers of the Tulip data visualization software.