Linked vis

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    .axis path, .axis line {
      stroke: #ccc;
    }
    .axis line {
      stroke-dasharray: 2;
    }
    .axis text {
      fill: #ccc;
    }

.state text {
      font-weight: 600;
    }
  </style>
</head>

<body>
  <script>
var width = 250;
var height = 200;
var margin = {top: 20, right: 30, bottom: 20, left: 30};
var xScale = d3.scaleLinear().range([0, width]);
var yScale = d3.scaleLinear().range([height, 0]);
var xAxis = d3.axisBottom()
	.scale(xScale)
	.ticks(5)
	.tickFormat(d => "'" + new String(d).slice(2))
	.tickSizeInner(-height)
	.tickSizeOuter(0)
	.tickPadding(6);
var yAxis = d3.axisLeft()
	.scale(yScale)
	.ticks(5)
	.tickFormat(d => d + '%')
	.tickSizeInner(-width)
	.tickSizeOuter(0)
	.tickPadding(6);
var line = d3.line()
	.x(d => xScale(d.year))
	.y(d => yScale(d.rate));
var red = '#d8472b';
var dispatch = d3.dispatch('load', 'yearchange');

d3.json('data.json', function(err, data) {
  var flatData = [];
  data.forEach(obj => {
    var year = +obj.date;
    for (key in obj) {
      if (key !== 'date' && key !== 'avg' && key !== 'D.C.') {
        var state = key;
        var rate = obj[key];
        flatData.push({
          year: year,
          state: state,
          rate: +rate,
        });
      }
    }
  });

// get the domain for scales
  var xDomain = d3.extent(flatData, d => d.year);
  var yDomain = d3.extent(flatData, d => d.rate);
  xScale.domain(xDomain);
  yScale.domain(yDomain).nice();

var dataByState = d3.nest()
    .key(d => d.state)
    .entries(flatData);

// create svg for each state
  var svg = d3.select('body')
    .selectAll('svg')
    .data(dataByState, d => d.state)
    .enter().append('svg')
      .attr('width', width + margin.left + margin.right)
      .attr('height', height + margin.top + margin.bottom)
      .append('g')
        .attr('transform', 'translate(' + [margin.left, margin.top] + ')');

dispatch.call('load', null, svg, dataByState);
  // default hovered year to 2016
  dispatch.call('yearchange', null, 2016);
});

// draw the static graph for each state
dispatch.on('load.graph', (svg, dataByState) => {

// draw axes
  svg.append('g')
    .classed('x axis', true)
    .attr('transform', 'translate(' + [0, height] + ')')
    .call(xAxis);
  svg.append('g')
    .classed('y axis', true)
    .call(yAxis);

// draw lines
  svg.append('path')
    .datum(d => d.values)
    .attr('d', line)
    .attr('stroke', red)
    .attr('stroke-width', 2)
    .attr('fill', 'none');
 	svg.append('rect')
  	.attr('width', width)
  	.attr('height', height)
  	.attr('opacity',0)
  	.on('mousemove',function(){
    	var [x, y] = d3.mouse(this);
    	var year = Math.round(xScale.invert(x)); 
    	dispatch.call('yearchange', null, year);
  });
});

dispatch.on('load.title', (svg) => {
  var title = svg.append('text');

dispatch.on('yearchange.title', year => {
    title.text(d => {
      var rate = d.values.find(d => d.year === year);
      rate = rate ? d3.format('.1f')(rate.rate) + '%' : 'N/A';
      return d.key + ' (' + rate + ')';
    })
  });
});

dispatch.on('load.point', svg => {
  var g = svg.append('g');

g.append('circle')
    .attr('fill', red)
    .attr('r', 5);

g.append('text')
    .attr('text-anchor', 'middle')
    .attr('font-size', 11);

dispatch.on('yearchange.point', year => {
    g.attr('transform', d => {
      var rate = d.values.find(d => d.year === year);
      return 'translate(' + [xScale(rate.year), yScale(rate.rate)] + ')';
    });
    g.select('text')
      .text(d => {
        var rate = d.values.find(d => d.year === year);
        return rate.year + ' (' + d3.format('.1f')(rate.rate) + '%)';
      });
  });
});
  </script>
</body>

https://d3js.org/d3.v4.min.js