function redraw() {
    if (!(year in data)) return;
    title.text(year);

    body.transition()
        .duration(750)
        .attr("transform", function(d) { return "translate(" + x(year - year1) + ",0)"; });

    years.selectAll("rect")
        .data(function(d) { return data[year][d] || [0, 0]; })
      .transition()
        .duration(750)
        .attr("height", y);
  }