query: SELECT ?country ?countryLabel ?population
  (GROUP_CONCAT(DISTINCT ?countryBLabel ; separator = ", ") AS ?similarPopulation)
  WHERE {
    ?country wdt:P31 wd:Q6256 .
    ?country wdt:P1082 ?population .
    ?countryB wdt:P31 wd:Q6256 .
    ?countryB wdt:P1082 ?populationB .
    FILTER (?country != ?countryB && ?populationB >= ?population * 0.95 && ?populationB <= ?population * 1.05)
    ?country rdfs:label ?countryLabel . FILTER (LANG(?countryLabel) = "en") .
    ?countryB rdfs:label ?countryBLabel . FILTER (LANG(?countryBLabel) = "en") .
  }
  GROUP BY ?country ?countryLabel ?population
  ORDER BY ?countryLabel