GDP deflator is an index of price changes of goods and services included in GDP.
\(\text{GDP deflator}=\frac { Nominal\ GDP }{ Real\ GDP } \times 100\)

(i) NDP = GDP - Depreciation.
(ii) NNP = GNP - Depreciation.
(iii) The difference between NDP and NNP is the net factor income from abroad.
(iv) In NDP it is excluded but in NNP it is included.

\(\mathrm{GNP}=\mathrm{C}+\mathrm{I}+\mathrm{G}+(\mathrm{X}-\mathrm{M})+(\mathrm{R}-\mathrm{P})\) or \(\mathrm{GNP}_{\mathrm{MP}}=\mathrm{GDP}_{\mathrm{MP}}\) + Net Factor income from Abroad.

"The labour and capital of a country acting on its natural resources produce annually a certain net aggregate of commodities, material and immaterial including services of all kinds. This is the true net annual income or revenue of the country or national dividend". - Alfred Marshall

(i) National income is of great importance for the economy of a country.
(ii) National income helps us to know the relative importance and contribution of each sector. We could find how income is produced, how it is distributed, how much is spent, saved or taxed.
(iii) National income data is used to build economic models in short run and long run.
(iv) Data regarding gross income, output, saving & consumption is used in economic planning.
(v) National income data is used to build economic models in short run and long run.
(vi) It is used to make international comparison, inter - regional comparison and inter - temporal comparison of growth of the economy during different periods.
(vii) If income is equally distributed, the per capita income will reflect the economic welfare of the country.

(i) The total expenditure incurred by the society in a particular year is added.
(ii) It includes personal consumption expenditure (C), net domestic investment (I), Government expenditure on consumption and capital goods (G) and net exports (X - M).
\(\mathrm{GNP}=\mathrm{C}+\mathrm{I}+\mathrm{G}+(\mathrm{X}-\mathrm{M})\)
(iii) Second hand goods, purchase of shares and bonds, transfer payments and expenditure on intermediate goods must not be included.

S.No	Personal Income	Disposable Income
1	It is the total income received by the individual before payment of direct taxes in a year	It is the individual's income after the payment of income tax
2		Disposable income = Personal income - Direct tax

1. The average income of a person of a country in a particular year is called Per Capita Income.
2. Per capita income is got by dividing national income by population.
Per capita income =\(\cfrac { National\ income }{ Population } \)

(i) National income is of great importance for the economy of a country.
(ii) National income helps us to know the relative importance and contribution of each sector. We could find how income is produced, how it is distributed, how much is spent, saved or taxed.
(iii) National income data is used to formulate monetary policy, fiscal policy and other policies.
(iv) Data regarding gross income, output, saving and consumption is uscd in economic planning.
(v) National income data is used to build economic models in short run and long run.
(vi) It is used to make international comparison, inter regional comparison and inter temporal comparison of growth of the economy during different periods.
(vii) If income is equally distributed, the per capita income will reflect the economic welfare of the country.