Annual global population growth for different periods

gistfile1.txt

const parseInput = input => {
  const lines = input.split('\n');
  const output = [];
  let periodStartDate = null;
  let periodStartPopulation = null;
  for (let i = 0; i < lines.length; i++) {
    const lineBits = lines[i].split(' ').filter(lineBit => lineBit !== '');
    if (i === 0) {
      periodStartDate = parseInt(lineBits[0]);
      periodStartPopulation = parseInt(lineBits[1]);
      continue;
    }
    const period = {
      startDate: periodStartDate,
      startPopulation: periodStartPopulation,
      endDate: parseInt(lineBits[0]),
      endPopulation: parseInt(lineBits[1]),
    };
    period.annualGrowthRate = 
      (
        Math.round(
        ( (period.endPopulation / period.startPopulation) - 1 )
        / (period.endDate - period.startDate) * 10000
        ) / 100
      ) + '%';
    output.push(period);

    if (i === lines.length - 1) {
      continue;
    }
    periodStartDate = parseInt(lineBits[0]);
    periodStartPopulation = parseInt(lineBits[1]);
  }
  return output;
};

const input = `-10000 4
-8000  5
-7000  5
-6000  5
-5000  5
-4000  7
-3000  14
-2000  27
-1000  50
-750   60
-500   100
-400   160
-200   150
1      170
200    190
400    190
500    190
600    200
700    210
800    220
900    226
1000   310
1100   301
1200   360
1250   400
1300   360
1340   443
1400   350
1500   425
1600   545
1650   470
1700   600
1750   790
1800   980
1850   1260
1900   1650
1910   1750
1920   1860
1930   2070
1940   2300
1950   2400
1960   3020
1970   3700
1974   4000
1980   4430
1987   5000
1990   5260
2000   6070
2017     7500`;

const output = parseInput(input);
console.log(output);