https://graph.facebook.com/v2.2/<APP ID>/app_insights?metric_key=initial_permission_grants

{
  "data": [
    {
      "time": "2014-12-12T08:00:00+0000",
      "value": "0"
    },
    {
      "time": "2014-12-13T08:00:00+0000",
      "value": "0"
    },
    {
      "time": "2014-12-14T08:00:00+0000",
      "value": "0"
    },
    {
      "time": "2014-12-15T08:00:00+0000",
      "value": "1"
    },
    {
      "time": "2014-12-16T08:00:00+0000",
      "value": "0"
    },
    {
      "time": "2014-12-17T08:00:00+0000",
      "value": "0"
    },
    {
      "time": "2014-12-18T08:00:00+0000",
      "value": "0"
    }
  ]
}