natural increase
Refers to population growth from births minus deaths, excluding migration. Common in demographic and economic discussions.
Japan's natural population increase is declining.
Population growth is the sum of natural increase and net migration.
人口増加 is the broader term for population growth, which can be broken down into 自然増 and 社会増.
Compound of 自然 (natural) and 増 (increase). The reading しぜんぞう follows standard on'yomi for both kanji.