This visualization displays global immigration numbers across multiple years, with proportional circles overlaid on a natural Earth projection map. Users can select different years from a dropdown menu to update the circle sizes. The React app uses d3.geoNaturalEarth1 with d3.geoPath to render country boundaries, graticules, and sphere from TopoJSON data, while d3.scaleSqrt scales circle radii for immigrant counts from the Sense Your City dataset.