Gross domestic product
A region's gross domestic product, or GDP, is one of the ways for measuring the size of its economy. The GDP of a country is defined as the total market value of all final goods and services produced within a country in a given period of time (usually a calendar year). It is also considered the sum of value added at every stage of production (the intermediate stages) of all final goods and services produced within a country in a given period of time. Until the 1992 the term GNP or gross national product was used in the United States. The two terms GDP and GNP are almost identical - and yet entirely different; GDP (or GDI - Gross Domestic Income) being concerned with the region in which income is generated.  That is, what is the market value of all the output produced in a nation, the United States, for example, in one year.  GDP concerns itself with where the output is produced and not who produced it.  Meanwhile, GNP (or GNI - Gross National Income) is a measure of the accrual of income or the value of the output, produced by the "nationals" of a region.  GNP concerns itself with who "owns" the production.  If we take the USA as an example again, GNP measures the value of output produced by American firms, regardless of where the firms are located.  This compares to GDP which is concerned with where the production takes place and not if the company is an American firm or not. Supposing that a firm can be defined as American in an economic world where most large firms are actually global groups.
The most common approach to measuring and understanding GDP is the expenditure method:
"Gross" means depreciation of capital stock is not included. With depreciation, with net investment instead of gross investment, it is the net domestic product.  Consumption and investment in this equation are the expenditure on final goods and services. The exports minus imports part of the equation (often called cumulative exports) then adjusts this by subtracting the part of this expenditure not produced domestically (the imports), and adding back in domestic area (the exports).
Economists (since Keynes) have preferred to split the general consumption term into two parts; private consumption, and public sector (or government) spending. Two advantages of dividing total consumption this way in theoretical macroeconomics are:
- Private consumption is a central concern of welfare economics. The private investment and trade portions of the economy are ultimately directed (in mainstream economic models) to increases in long-term private consumption.
- If separated from endogenous private consumption, government consumption can be treated as exogenous, so that different government spending levels can be considered within a meaningful macroeconomic framework.

# Measuring GDP

## The components of GDP
Each of the variables C, I, G and NE (where GDP = C + I + G + NE as above):
(Note: - GDP is sometimes also referred to as Y in reference to a GDP graph)
- C is private consumption in the economy. This includes most personal expenditures of households such as food, rent, medical expenses and so on but does not include new housing.
- I is defined as business investments in capital. Examples of investment by a business include construction of a new mine, purchase of software, or purchase of machinery and equipment for a factory.  Spending by households on new houses is also included in Investment. Unlike general meaning, 'Investment' in GDP is meant very specifically as non-financial product purchases. Buying financial products is classed as 'saving' , as opposed to investment. The distinction is (in theory) clear: if money is converted into goods or services, it is investment; but, if you buy a bond or a share, this transfer payment is excluded from the GDP sum. Although such purchases would be called investments in normal speech, from the total-economy point of view, this is simply swapping of deeds, and not part of the real economy or the GDP formula.
- G is the sum of government expenditures on final goods and services. It includes salaries of public servants, purchase of weapons for the military, and any investment expenditure by a government. It does not include any transfer payments, such as social security or unemployment benefits.
- X is gross exports. GDP captures the amount a country produces, including goods and services produced for overseas consumption, therefore exports are added.
- M is gross imports. Imports are subtracted since imported goods will be included in the terms G, I, or C, and must be deducted to avoid counting foreign supply as domestic.
- NE are "net exports" in the economy: gross exports  gross imports. There is a fixed relation: NE = X  M.
It is important to understand the meaning of each variable precisely in order to:
- Read national accounts.
- Understand Keynesian or neo-classical macroeconomics.

## Examples of GDP component variables
Examples of C, I, G, & NX: If you spend money to renovate your hotel so that occupancy rates increase, that is private investment, but if you buy shares in a consortium to do the same thing it is saving. The former is included when measuring GDP (in I), the latter is not. However, when the consortium conducted its own expenditure on renovation, that expenditure would be included in GDP.
If the hotel is your private home your renovation spending would be measured as Consumption, but if a government agency is converting the hotel into an office for civil servants the renovation spending would be measured as part of public sector spending (G).
If the renovation involves the purchase of a chandelier from abroad, that spending would also be counted as an increase in imports, so that NX would fall and the total GDP is unaffected by the purchase. (This highlights the fact that GDP is intended to measure domestic production rather than total consumption or spending. Spending is really a convenient means of estimating production.)
If you are paid to manufacture the chandelier to hang in a foreign hotel the situation would be reversed, and the payment you receive would be counted in NX (positively, as an export). Again, we see that GDP is attempting to measure production through the means of expenditure; if the chandelier you produced had been bought domestically it would have been included in the GDP figures (in C or I) when purchased by a consumer or a business, but because it was exported it is necessary to 'correct' the amount consumed domestically to give the amount produced domestically. (As in Gross Domestic Product.)

## The GDP income account
Another way of measuring GDP is to measure the total income payable in the GDP income accounts. In this situation, one will sometimes hear of Gross Domestic Income (GDI), rather than Gross Domestic Product.  This should provide the same figure as the expenditure method described above. (By definition, GDI=GDP. In practice, however, measurement errors will make the two figures slightly off when reported by national statistical agencies.)
The formula for GDP measured using the income approach, called GDP(I), is:
- Compensation of employees (COE) measures the total remuneration to employees for work done. It includes wages and salaries, as well as employer contributions to social security and other such programs.
- Gross operating surplus (GOS) is the surplus due to owners of incorporated businesses. Often called profits, although only a subset of total costs are subtracted from gross output to calculate GOS.
- Gross mixed income (GMI) is the same measure as GOS, but for unincorporated businesses. This often includes most small businesses.
The sum of COE, GOS and GMI is called total factor income, and measures the value of GDP at factor (basic) prices.The difference between basic prices and final prices (those used in the expenditure calculation) is the total taxes and subsidies that the Government has levied or paid on that production. So adding taxes less subsidies on production and imports converts GDP at factor cost to GDP(I).
Another formula can be written as this:
GDP = R + I + P + SA + W
where R = rents      I = interests      P = profits      SA = statistical adjustments (corporate income taxes, dividends, undistributed corporate profits)      W = wages

# Measurement

## International standards
The international standard for measuring GDP is contained in the book System of National Accounts (1993), which was prepared by representatives of the International Monetary Fund, European Union, Organization for Economic Co-operation and Development, United Nations and World Bank. The publication is normally referred to as SNA93, to distinguish it from the previous edition published in 1968 (called SNA68).
SNA93 sets out a set of rules and procedures for the measurement of national accounts. The standards are designed to be flexible, to allow for differences in local statistical needs and conditions.

## National measurement
Within each country GDP is normally measured by a national government statistical agency, as private sector organizations normally do not have access to the information required (especially information on expenditure and production by governments).
- Argentina: Instituto Nacional de Estadistica y Censos (INDEC)
- Australia: Australian Bureau of Statistics (ABS), Reserve Bank of Australia (RBA).
- Austria: Statistik Austria.
- Bangladesh: Bangladesh Bureau of Statistics
- Belgium: Directorate-general Statistics Belgium
- Brazil: Instituto Brasileiro de Geografia e Estatistica (IBGE).
- Bulgaria:   , National Statistical Insitute (NSI).
- Chile: Instituto Nacional de Estadisticas (INE).
- Colombia: Departamento Administrativo Nacional de Estadistica (DANE).
- Croatia: Central Bureau of Statistics (CROSTAT).
- Canada: Statistics Canada (StatCan).
- Cyprus:      (CYSTAT).
- Czech Republic: Cesky statisticky urad (CSU).
- Denmark: Danmarks Statistik.
- Dominican Republic: Central Bank of the Dominican Republic
- Estonia: Eesti Statistikaamet
- Finland: Tilastokeskus.
- France: Institut National de la Statistique et des Etudes Economiques (INSEE).
- Germany: Statistisches Bundesamt
- Greece:     ().
- Hong Kong:Census and Statistics Department
- Hungary: Hungarian Central Statistical Office
- Iceland: Statistics Iceland.
- Ireland Central Statistics Office
- India: Government of India Ministry of Statistics and Programme Implementation.
- Indonesia: Badan Pusat Statistik (BPS).
- Israel: Israel Central Bureau of Statistics
- Italy: Istituto Nazionale di Statistica (ISTAT).
- Japan: Ministry of Economy, Trade and Industry (METI) .
- Jamaica: [/ Statistical Institute of Jamaica (STATIN)
- Korea (South): National Stastical Office, Republic of Korea (NSO).
- Latvia: Centrala statistikas parvalde
- Lithuania: Lietuvos Statistikos Departamentas (Department of Statistics, Lithuania).
- Luxembourg: Service central de la statistique et des etudes economiques (Luxembourg Statistics).
- Malaysia: Jabatan Perangkaan Malaysia (Department of Statistics, Malaysia)
- Macau: Direccao dos Servicos de Estatistica e Censos (DSEC).
- Mexico: Instituto Nacional de Estadistica, Geografia e Informatica (INEGI).
- The Netherlands: Centraal Bureau voor de Statistiek (Statistics Netherlands).
- New Zealand: Statistics New Zealand (Statistics New Zealand - Tatauranga Aotearoa).
- Norway: Statistisk Sentralbyra
- Pakistan: Federal Bureau of Statistics.
- Peru: Instituto Nacional de Estadistica e Informatica (INEI).
- Philippines Philippine National Statistical Coordination Board
- Poland Central Statistical Office (Gowny Urzad Statystyczny; GUS)
- Portugal Instituto nacional de Estatistica (National Statistics Office).
- Romania Institutul National de Statistica
- Russia: Federal Service of State Statistics (Rosstat).
- Serbia: Republicki zavod za statistiku
- Singapore: Statistics Singapore
- Slovakia: Statisticky urad SR.
- Slovenia: Statisticni urad Republike Slovenije (SURS).
- South Africa: Statistics South Africa (STATSSA).
- Spain: Instituto Nacional de Estadistica (INE).
- Sweden: Statistiska Centralbyran (SCB).
- Switzerland: Swiss Statistics.
- Turkey: Turkiye Istatistik Kurumu (TUIK).
- United Kingdom: Office for National Statistics (ONS).
- United States: Bureau of Economic Analysis (BEA).
- Venezuela: Instituto Nacional de Estadistica (INE).
- Vietnam: General Statistics Office (GSO).
GDP can measure spending on all goods and services.
GDP can also measure all income earned.

## Interest rates
Net interest expense is a transfer payment in all sectors except the financial sector. Net interest expenses in the financial sector is seen as production and value added and is added to GDP.
Peru: Instituto de Estadisticas e Informatica - INEI

# Cross-border comparison
The level of GDP in different countries may be compared by converting their value in national currency according to either
- current currency exchange rate: GDP calculated by exchange rates prevailing on international currency markets
- purchasing power parity exchange rate: GDP calculated by purchasing power parity (PPP) of each currency relative to a selected standard (usually the United States dollar).
The relative ranking of countries may differ dramatically between the two approaches.
- The current exchange rate method converts the value of goods and services using global currency exchange rates. This can offer better indications of a country's international purchasing power and relative economic strength. For instance, if 10% of GDP is being spent on buying hi-tech foreign arms, the number of weapons purchased is entirely governed by current exchange rates, since arms are a traded product bought on the international market (there is no meaningful 'local' price distinct from the international price for high technology goods).
- The purchasing power parity method accounts for the relative effective domestic purchasing power of the average producer or consumer within an economy. This can be a better indicator of the living standards of less-developed countries because it compensates for the weakness of local currencies in world markets. (For example, India ranks 13th by GDP but 4th by PPP.)The PPP method of GDP conversion is most relevant to non-traded goods and services.
There is a clear pattern of the purchasing power parity method decreasing the disparity in GDP between high and low income (GDP) countries, as compared to the current exchange rate method. This finding is called the Penn effect.
For more information see measures of national income.

# GDP and standard of living
GDP per capita is often used as an indicator of standard of living in an economy. While this approach has advantages, many criticisms of GDP focus on its use as a sole indicator of standard of living.
The major advantages to using GDP per capita as an indicator of standard of living are that it is measured frequently, widely and consistently; frequently in that most countries provide information on GDP on a quarterly basis (which allows a user to spot trends more quickly), widely in that some measure of GDP is available for practically every country in the world (allowing crude comparisons between the standard of living in different countries), and consistently in that the technical definitions used within GDP are relatively consistent between countries, and so there can be confidence that the same thing is being measured in each country.
The major disadvantage of using GDP as an indicator of standard of living is that it is not, strictly speaking, a measure of standard of living. GDP is intended to be a measure of particular types of economic activity within a country. Nothing about the definition of GDP suggests that it is necessarily a measure of standard of living. For instance, in an extreme example, a country which exported 100 per cent of its production and imported nothing would still have a high GDP, but a very poor standard of living.
The argument in favour of using GDP is not that it is a good indicator of standard of living, but rather that (all other things being equal) standard of living tends to increase when GDP per capita increases. This makes GDP a proxy for standard of living, rather than a direct measure of it. GDP per capita can also be seen as a proxy of labor productivity. As the productivity of the workers increases, employers must compete for them by paying higher wages. Conversely, if productivity is low, then wages must be low or the businesses will not be able to make a profit.
There are a number of controversies about this use of GDP.

# Criticisms and limitations
GDP is widely used by economists to follow how the economy is moving, as its variations are relatively quickly identified. However, its value as an indicator for the standard of living is considered to be limited. An alternative for this purpose is the United Nations' Human Development Index in which the GDP is a contributing factor in its calculation. Criticisms of how the GDP is used include:
- One main problem in estimating GDP growth over time is that the purchasing power of money varies in different proportion for different goods, so when the GDP figure is deflated over time, GDP growth can vary greatly depending on the basket of goods used and the relative proportions used to deflate the GDP figure. For example, in the past 80 years the GDP per capita of the United States if measured by purchasing power of potatoes, did not grow significantly. But if it is measured by the purchasing power of eggs, it grew several times.
- Official GDP estimates may not take into account the black market, where the money spent is not registered, and the non-monetary economy, where no money comes into play at all, resulting in inaccurate or abnormally low GDP figures. For example, in countries with major business transactions occurring informally, portions of local economy are not easily registered. Bartering may be more prominent than the use of money, even extending to services (I helped you build your house ten years ago, so now you help me).
- This mainstream economic analysis ignores externalities such as the environment, subsistence production and domestic work. The current system counts oil spills and wars as contributors to economic growth, while child-rearing and housekeeping are deemed valueless. The work of New Zealand economist, Marilyn Waring, has highlighted that if a concerted attempt to factor in unpaid work were made, then it would in part, undo the injustices of unpaid (and in some cases, slave) labour, and also provide the political transparency and accountability necessary for democracy. Also, when GDP is used as a measure of success over time, the amount of housework that was done 50 years ago compared to the present time is much greater. Thus, comparing GDP over time cannot take into account the changes in society and lifestyle.
- It ignores volunteer, unpaid work. For example, Linux contributes nothing to GDP, but it was estimated that it would have cost more than a billion US dollars for a commercial company to develop.  Wikipedia, an open-source online encyclopedia, is another good example.
- Very often different calculations of GDP are confused among each other. For cross-border comparisons one should especially regard whether it is calculated by purchasing power parity (PPP) method or current exchange rate method. Using the latter method to compare living standards is problematic, since it does not always reflect the real wealth of the citizens, ie. how much they are able purchase locally in relation to their income (see Penn effect).
- Cross-border comparisons of GDP can be inaccurate as they do not take into account local differences in the quality of goods, even when adjusted for purchasing power parity. This type of adjustment to an exchange rate is controversial because of the difficulties of finding comparable baskets of goods to compare purchasing power across countries. For instance, people in country A may consume the same number of locally produced apples as in country B, but apples in country A are of a more tasty variety. This difference in material well being will not show up in GDP statistics. This is especially true for goods that are not traded globally, such as housing.
- GDP counts work that produces no net change or that results from repairing harm. For example, rebuilding after a natural disaster or war may produce a considerable amount of economic activity and thus boost GDP, but it would have been far better if the disaster had never occurred in the first place. The economic value of health care is another classic exampleit may raise GDP if many people are sick and they are receiving expensive treatment, but it is not a desirable situation. Alternative economic measures, such as the standard of living or discretionary income per capita better measure the human utility of economic activity. See uneconomic growth.
- Quality of lifehuman happinessis determined by many other things than physical goods and services. Even the alternative economic measures of standard of living and discretionary income do not take these factors into account.
- Cross border trade within companies distorts the GDP and is done frequently to escape high taxation. Examples include the German Ebay that evades German tax by doing business in Switzerland, and American companies that have founded holdings in Ireland to "buy" their own products for cheap from their continental factories (without shipping) and selling them for profit via Ireland - thereby reducing their taxes and increasing Irish GDP.
- People may buy cheap, low-durability goods over and over again, or they may buy high-durability goods less often. It is possible that the monetary value of the items sold in the first case is higher than that in the second case, in which case a higher GDP is simply the result of greater inefficiency and waste. (This is not always the case; durable goods are often more difficult to produce than flimsy goods, and consumers have a financial incentive to find the cheapest long-term option. With goods that are undergoing rapid change, such as in fashion or high technology, the short lifespan may increase customer satisfaction by allowing them to have newer products.)
- GDP does not measure the sustainability of growth. A country may achieve a temporarily high GDP by over-exploiting natural resources or by misallocating investment. For example, the large deposits of phosphates gave the people of Nauru one of the highest per capita incomes on earth, but since 1989 their standard of living has declined sharply as the supply has run out. Oil-rich states can sustain high GDPs without industrializing, but this high level would no longer be sustainable if the oil runs out. Economies experiencing an economic bubble, such as a housing bubble or stock bubble, or a low private-saving rate tend to appear to grow faster due to higher consumption, mortgaging their futures for present growth. Economic growth at the expense of environmental degradation can end up costing dearly to clean up; GDP does not account for this.
- As a measure of actual sale prices, GDP does not capture the economic surplus between the price paid and subjective value received, and can therefore underestimate aggregate utility.
- The annual growth of real GDP is adjusted by using the "GDP deflator", which tends to underestimate the objective differences in the quality of manufactured output over time. (The deflator is explicitly based on subjective experience when measuring such things as the consumer benefit received from computer-power improvements since the early 1980s). Therefore the GDP figure may underestimate the degree to which improving technology and quality-level are increasing the real standard of living.
- GDP does not take disparity in incomes between the rich and poor into account. See income inequality metrics for discussion of a variety of complementary economic measures.
- GDP is often incorrectly used in (often unscientific and unrealistic) comparisons where net national worth (or national wealth) would be a more correct point of reference. For example, "person X could buy country Y, because his/her wealth is more than the GDP of that country". Net national worth is often equal to several years cumulative GDP  .
The limits of GDP (or GNP, a slightly different notion) can be summed up in the words of two critics. Robert Kennedy said:
The gross national product includes air pollution and advertising for cigarettes and ambulances to clear our highways of carnage. It counts special locks for our doors and jails for the people who break them. GNP includes the destruction of the redwoods and the death of Lake Superior. It grows with the production of napalm, and missiles and nuclear warheads... it does not allow for the health of our families, the quality of their education, or the joy of their play. It is indifferent to the decency of our factories and the safety of our streets alike. It does not include the beauty of our poetry or the strength of our marriages, or the intelligence of our public debate or the integrity of our public officials. It measures everything, in short, except that which makes life worthwhile.
The second critic, Simon Kuznets the inventor of the GDP, in his very first report to the US Congress in 1934 said:
...the welfare of a nation  scarcely be inferred from a measure of national income...
In 1962, Kuznets stated:
Distinctions must be kept in mind between quantity and quality of growth, between costs and returns, and between the short and long run. Goals for more growth should specify more growth of what and for what.
Some economists have attempted to create a replacement for GDP called the Genuine Progress Indicator (GPI), which attempts to address many of the above criticisms. Many nations calculate a national wealth, a sum of all assets in a nation, but this again does not account for future obligations such as environmental degradation, asset bubbles, and debt. Other nations such as Bhutan have advocated gross national happiness as a standard of living. (Bhutan claims to be the world's happiest nation.)

# Lists of countries by their GDP
- List of countries by GDP (nominal), (per capita)
- List of countries by GDP (PPP), (per capita), (per hour)
- List of countries by GDP demographics comparison
- List of countries by GDP (real) growth rate, (per capita)
- List of countries by GDP sector composition
- List of countries by future GDP estimates (PPP), (per capita), (nominal)
- List of countries by past GDP (PPP), (nominal)