Primary sector includes agriculture, forestry, animal husbandry, fishing, poultry farming, and mining. Quarrying and manufacturing is included in the secondary sector.

The importance of each sector in a country's economy has changed over time, with developed countries shifting from the primary and secondary sectors to the tertiary sector, and developing countries seeing a growth in the services sector:

Developed countries

In developed countries, the primary sector was the main economic activity in the early stages of development. As industrialization took place, the secondary sector (manufacturing and industries) became more important. However, the tertiary sector (services) has since become the most important sector in developed countries, employing the majority of the workforce.

Developing countries

In developing countries, the primary sector is still the primary focus, with most people employed in agriculture and food production. However, the services sector has been growing faster than manufacturing in many developing economies over the past three decades. In 2019, the services sector accounted for 55% of GDP and 45% of employment in developing economies.

Each sector is interdependent on the other so that the economy as a whole functions properly and efficiently. The primary sector is where the materials for the secondary sector are gathered. In the secondary sector, the product is then made into consumable item(s) which is then distributed by the tertiary sector.

Governments can make subsidies, taxing the general and giving the money to an industry, or tariffs, adding taxes to foreign products to raise prices and make domestic products more alluring. Higher taxes, fees, and greater regulations can impede businesses or entire industries.

The primary, secondary, and tertiary sectors of the economy can have different environmental impacts:

Primary sector

This sector involves extracting raw materials like coal, iron, wood, and corn. Activities like mining, agriculture, fishing, and forestry can deplete and degrade natural resources.

Secondary sector

This sector involves manufacturing goods from raw materials. Activities like recycling and waste management can help reduce environmental impact. However, industrial practices like burning coal or natural gas can release pollutants that harm human health and ecosystems.

Tertiary sector

This sector involves providing services like education, healthcare, and eco-tourism. The tertiary sector can contribute to sustainable development.

Diversification increases with increasing population as local firms have access to a larger market and thus benefit from economies of scale. Human capital allows economies to change their specialization patterns from primary commodities towards more knowledge- intensive manufactured goods.