public static function makeEmptyRow()
    {
        return array(Metrics::INDEX_NB_UNIQ_VISITORS    => 0,
                     Metrics::INDEX_NB_VISITS           => 0,
                     Metrics::INDEX_NB_ACTIONS          => 0,
                     Metrics::INDEX_NB_USERS            => 0,
                     Metrics::INDEX_MAX_ACTIONS         => 0,
                     Metrics::INDEX_SUM_VISIT_LENGTH    => 0,
                     Metrics::INDEX_BOUNCE_COUNT        => 0,
                     Metrics::INDEX_NB_VISITS_CONVERTED => 0,
        );
    }