Plot.plot({
y: {
grid: true,
label: "↑ Travelers per day (millions)",
transform: (d) => d / 1e6
},
marks: [
Plot.ruleY([0]),
Plot.line(travelers, {x: "date", y: "previous", strokeOpacity: 0.5}),
Plot.line(travelers, {x: "date", y: "current"}),
Plot.text(travelers, Plot.selectFirst({x: "date", y: "previous", text: ["2019"], fillOpacity: 0.5, lineAnchor: "bottom", dy: -6})),
Plot.text(travelers, Plot.selectFirst({x: "date", y: "current", text: ["2020"], lineAnchor: "top", dy: 6}))
]
})