Stacked Area Chart

{
  "$schema": "https://vega.github.io/schema/vega-lite/v2.json",
  "description": "Area chart showing weight of cars over time.",
  "width": 300, "height": 200,
  "data": {"url": "data/unemployment-across-industries.json"},
  "mark": "area",
  "encoding": {
    "x": {
      "timeUnit": "yearmonth", "field": "date", "type": "temporal",
      "axis": {"format": "%Y"}
    },
    "y": {
      "aggregate": "sum", "field": "count", "type": "quantitative"
    },
    "color": {
      "field": "series",
      "type": "nominal",
      "scale": {"scheme": "category20b"}
    }
  }
}