This bar chart visualizes the top 20 countries by population in 2010, sourced from a CSV file fetched via `d3.csv`. The chart uses a horizontal bar layout, with the `d3.scaleBand` y-axis for country names and a `d3.scaleLinear` x-axis for population values. Blue rectangles (`#4a90e2`) represent each country, with axes rendered using `d3.axisLeft` and `d3.axisBottom`, the latter formatted with `.tickFormat(d3.format('.2s'))`. Population data is sorted in descending order before slicing to the top 20.