Price and Volume Measures

Transcription

1 Price and Volume Measures 1 Third Intermediate-Level e-learning Course on 2008 System of National Accounts May - July 2014

2 Outline 2 Underlying Concept Deflators Price indices Estimation and SNA Guidelines

3 Lesson Objectives 3 At the end of this lesson the participant will be able to: Describe the process of price and volume change in national accounts Describe the process of constant price estimation Apply concepts of deflators to generate constant price measures

4 4 Why do we need price and volume measures? To interpret changes in nominal values when relative prices and/or general price level are changing. For goods and services - when nominal values of goods and services transacted (imported, consumed, produced, exported, etc) change How much is due to changes in the prices How much is due to changes in quantity and quality Purchasing power parities and Real Income Measures

5 5 Current vs. Constant Tolu Republic

6 Current vs. Constant Tolu Republic (2) = 5% constant price growth, 10% current price growth 6% CPI growth

7 Price, Quantity, Value and Volume 7 means"change in" price index at time quantity (volume) at time price at time value at time where : 1 1 = = = = = = = t I t Q t P t V Q P Q P Q Q P I I V Q P V t t t t t t t t t t t t t t t t t t

8 8 Price, Quantity, Value and Volume Quantity: Unit for measuring the amount of a good or service, i.e Kg., tonne, units quantities are only truly additive at the single product level Price: Value of one unit of a good or service (of the same quality)! An average of the prices of different goods or services should not be used to measure price changes over time

9 9 Price, Quantity, Value and Volume Volume is not same as Quantity. Changes in volume can occur as a result of changes in product-mix (or quality) Example: Mobile Phone production Model A Model B Total Price per unit Production in Production in Total value in Total value in

10 10 Price, Quantity, Value and Volume Unit value in 2001=8750/45= Unit value in 2002=11000/45= Change in volume: 11000/8750=1.26 (or 26%) Change in quantity: 45/45=0 Change in prices: 0 (prices remain unchanged) Change in unit values=244.44/194.44=1.1 (26%) We conclude Unit values are affected by the change in product mix. Change in product mix=change in average quality The term volume is preferred to quantity

11 Deflators 11 Various price indices can be used as deflators Deflators/Price indices allow for the comparison of two (or more) sets of prices for a common group of items To compare sets of prices One set needs to be the reference set and another the comparison set The price index for the reference set is usually given a index value of 100 or 1000

12 12 Why are deflators required? To interpret changes in nominal values when relative prices and/or general price level are changing. Carry out analyses of inflation, Measurement of real income, GDP,etc Indexation of wages, contracts, pensions

13 Why are deflators required 13 For goods and services - when nominal values of goods and services transacted (imported, consumed, produced, exported, etc) change How much is due to changes in the prices of the products; How much is due to changes in quantity and quality.

14 Types of deflators 14 Consumer price indices Producer price indices Export and import price indices Sectoral price indices

15 Main Types of Price Indices 15 Consumer price indices (CPI) Measure of average price change on goods and services acquired by the households for consumption Most common deflator in NA but has many issues for consideration Restricted to household goods and services Data quality issues

16 Main Types of Price Indices 16 Producer Price Index (PPI) Output PPIs measure the price change on products (goods and services) sold by the producers Input PPIs measure the price change on products acquired as intermediate input by the producers Domestic industrial production (manufacturing and public utilities) Might include mining, agriculture and transport Reflects changes in basic or producers prices

17 Main Types of Price Indices 17 Import Price Index Merchandise trade imports Captures changes in basic prices plus charges for insurance and freight (CIF) Sample survey of main importers vs. customs records Possibility of constructing a sub-index of particular imported products not available in CPI i.e fuels, cement Export Price Index Merchandise trade exports Depicts changes in basic prices or prices free on board (FOB) Sample survey (exporters/quarantine) vs. customs records

18 Main Types of Price Indices 18 Wholesale Price Index Sales of primary, intermediate and finished goods and services by wholesalers Reflects changes in producers prices, wholesalers trade margins and taxes on products levied on sales between producers and wholesalers May reflect purchasers prices for products sold to final users Based on price indices for commodities sold rather than industry of output Includes imports

19 Main Types of Price Indices 19 Building and construction price indices Measures changes in prices of construction materials/buildings of certain category Very difficult index to construct given the variation of construction

20 Deflator Compilation Techniques 20 Price Indices Price/Quantity p i,0 p i,t Price Indices q i,o Σ i p i,0 q i,0 Σ i p i,t q i,0 Σ i p i,t q i,0 / Σ i p i,0 q i,0 (Laspeyres) q i,t Σ i p i,0 q i,t Σ i p i,t q i,t Σ i p i,t q i,t / Σ i p i,0 q i,t (Paasche) Volume indices: Σ i p i,0 q i,t / Σ i p i,0 q i,0 Σ i p i,t q i,t / Σ i p i,t q i,0 (Laspeyres) (Paasche)

21 The Laspeyres Price Index 21 Fixes quantities from the base period Compares base period quantities valued in current period with base period quantities valued in the base period "How much more would I have to pay in the current period if I bought the same goods in the current period as I did in the base period?"

22 Example 1- Price and Quantity 22 Data PRICES FOR SIX COMMODITIES (PERIOD 0 AND PERIOD 1) Price in period ($) Commodity 0 1 A Agricultural commodity B Energy C Traditional manufacture D High-tech goods E Traditional services F High-tech services t p A t p B t p C t p D t p E t p F TABLE QUANTITIES FOR SIX COMMODITIES (PERIOD 0 AND PERIOD 1) Quantity in period Commodity 0 1 A Agricultural commodity B Energy C Traditional manufacture D High-tech goods E Traditional services F High-tech services t q A t q B t q C t q D t q E t q F

23 Example 1 cont d: Laspeyres Compilation revalue base period quantities 23 VALUE OF A BASKET FIXED USING PERIOD 0 QUANTITIES (QUANTITIES FROM PERIOD 0, PRICES FROM PERIODS 0 AND 1) Quantity Prices and values ($ s) Commodity Period 0 Period 1 q 0 p 0 p 0 q 0 p 1 p 1 q 0 A Agricultural commodity B Energy C Traditional manufacture D High-tech goods E Traditional services F High-tech services Total Laspeyres price index I 0:1 Laspeyres = 6 i= 1 6 i= 1 p p 1 i 0 i q q 0 i 0 i 100 $ $ $ $ $ $ = 100 $ $ $ $ $ $ $14.20 = 100 $10.00 = 142.0

24 Laspeyres price index 24 Example 2: Can also be compiled using expenditure weights if quantity data is not available Year 0 Year 1 Price/ unit Quantity Value Weight (%) Price/u nit Quantity Value Weight (%) A B LP 0 1 = (40/20)* (20/10)*.333 = = 2

25 The Paasche price index 25 Fixes quantities from the current period Compares current period quantities valued in current period with current period quantities valued in the base period "How much more would I have to pay in the current period if I bought the same goods in the base period as I did in the current period?"

26 Paasche revalue current period 26 quantities VALUE OF A BASKET FIXED USING PERIOD 1 QUANTITIES (QUANTITIES FROM PERIOD 1, PRICES FROM PERIODS 0 AND 1) Quantity Prices and values ($ s) Commodity Period 0 Period 1 q 1 p 0 p 0 q 1 p 1 p 1 q 1 A Agricultural commodity B Energy C Traditional manufacture D High-tech goods E Traditional services F High-tech services Total pi qi Paasche 0:1 price index i= 1 I = Paasche p q i= 1 i i $ $ $ $ $ $ = 100 $ $ $ $ $ $ $14.10 = 100 $10.20 = 138.2

27 The Fisher Ideal Price Index 27 A geometric mean of the Laspeyres and the Paasche I 0: t Fisher = I 0: t Laspeyres I 0: t Paasche = 1 ( I 0: t I 0: t Laspeyres Paasche)2

28 Geometric mean? 28 The geometric mean takes a product of n terms and then takes the n-th root For two terms, this is just the square root For three terms, the cube root This is particularly attractive when dealing with ratios If one product is 5/4 of its old price, and other is 4/5, what is the average price change?

29 Arithmetic mean = = 2 20 =

30 Geometric mean = = 1

31 The Fisher Ideal Price Index 31 From Example 1 we have the Fischer Index as I 0:1 Fisher = I 0:1 I 0:1 Laspeyres Paasche = = = 19,

32 The Fisher Ideal Price Index < < :1 Paasche 0:1 Fisher I < I < I 0:1 Laspeyres

33 Constant Prices 33 Changes in values of flows at current prices can be decomposed into: - Changes in their prices - Changes in the volumes Therefore if prices are kept constant over time, the values are said to be in volume terms

34 What is meant by Value(s) at Constant 34 Prices It is the value(s) of a product(s) for the current period using its own price(s) from an earlier period. Constant prices can be generated through Price Deflation Volume extrapolation Quantity revaluation This concept is illustrated in table below:

35 35 What is meant by Value(s) at Constant Prices Year 0 Year 1 Price Per unit Quantity Value Price Per unit Quantity Value Constant (year 0) Value (1) (2) (3) = (1)*(2) (4) (5) (6)=(4)*(5) (7)=(1)*(5) A B Tot Value increase = 1080/450 = 140% Price increase for both items = 100% Constant price increase = 540/450 = 20%

36 Estimation Methods in General 36 Three methods of deriving constant price measures Price deflation divide a current price value by a suitable price index Quantity revaluation volumes times price, may be used for current price estimates or constant price estimates Volume extrapolation extrapolate base year value by a volume index (for some people, there is only price deflation)

37 Controversy? 37 GDP at constant prices is derived as the sum of expenditure components or value added of products at constant prices Expenditure components of GDP are aggregates of transactions that can be compiled by observing and recording actual transactions Value of these transactions can be factored into their own prices and quantities Therefore, better measures of price and volume for GDP conceptually may be obtained from the expenditure approach (cf. production approach) Commonly, price deflation of current values is used to derive the data at constant prices for expenditure items, although extrapolation by volume index is also used

38 Reference, Base and Weight Periods 38 Reference period (comparison period): The period in an index number time series taken as = 100 (1000) Base period (pricing period) Price base period: The period whose prices are used as denominators in calculating price relatives Pt/Po (o is the price base period) Quantity base period: The period whose quantities are used as denominators in calculating quantity relatives Qt/Qo (o is the quantity base period) Weight period: The period from which the weights are taken

39 Change of Base Year 39 Growth rate (percent) Values in current prices Pork Price Quantity Value Beef Price Quantity Value TOTAL Value

40 Change of Base Year (contd.) 40 Effects on growth rates: Growth rate (percent) Values in constant prices of 1980 Pork Beef TOTAL Values in constant prices of 1985 Pork Beef TOTAL Values in constant prices of 1990 Pork Beef TOTAL

41 41 Choice of base year in the national accounts and chaining Choice of base year? Weights need to be relevant for nearby years A normal year? (could be different from reference year) Why change base year? Structural changes in production structure examples? Structural changes in consumption patterns Structural changes in relative prices examples? Appearance of new products examples? Disappearance of old products Significant quality changes examples?

42 42 Choice of base year in the national accounts and chaining (contd.) For all these reasons, goods and services are not comparable between periods that are too far apart How far is too far five years? Same issues for price indexes as for national accounts CPI also needs to be rebased regularly and frequently What to do? Annual Chain. Even better, chain with superlative indices such as the Fisher and Törnqvist (NB rebasing base weighted series is a type of chaining, but with links equal to the number of years between base years)

43 Rebasing What is Involved? 43 Choose a base year As recent as possible With all the necessary data Often follows => HIES => CPI rebase => NA rebase Important long term planning issue (agreed at HOPS 2010) What data are needed? Current price value data at the level of detail needed Price index data (re-expressed to the NA base year) Existing constant price series up to date, along with all underlying data

44 Main SNA Recommendations for Price and Volume Measures: GDP and Other Aggregates 44 Traditional Method Constant price estimates for GDP and its components, with corresponding (implicitly) Paasche price indices Change of base every 5-10 years Re-basing of whole time series Re-basing of limited period (with implicit or explicit chain-linking) State of the art Ideal method Annually chained Fischer price and volume indices for GDP and its components Calculate in a supply-use framework Second best: Annually chained Laspeyres volume indices and Paasche price indices OR Annually chained Paasche volume indices and Laspeyres Price indices

45 Fundamental Principles 45 #1 the more detail the better (for price and volume measures) #2 volume measures at the detailed level should be aggregated using Laspeyres formula, prices using Paasche formula #3 volume measures at the detailed level should be aggregated using the previous year s prices => chain volume measures (Eurostat Manual on price and volume measures in national accounts)

46 Questions for CPI Users 46 Is your CPI as good as it should be? Is coverage good enough for NA purposes? Regional coverage Product coverage e.g., telecommunications, hotels and restaurants and other tourist products... Plans for improvement Quality improvements to existing indexes? New indexes PPI, wages (especially government), export or import...? If have plans, how to develop?

47 GDDS Plans for Improvement 47 Fiji rebase CPI to 2002 (metadata = 2002!!!) Kiribati do HIES to rebase CPI PNG rebase CPI from to 2012 Samoa rebase to 2014, extend coverage, use COICOP Solomons rebase after 2011 HIES, add two towns, improve timeliness Timor-Leste proposed new indexes PPI, X/M, labour Tonga extend coverage Tuvalu change from quarterly to monthly Vanuatu conduct HIES to rebase CPI (metadata = 2004!!!)

48 48 Laspeyres price index Year 0 Year 1 Price/ unit Quantity Value Weight (%) Price/u nit Quantity Value Weight (%) A B LP 0 1 = (40/20)* (20/10)*.333 = = 2

49 Paasche Price Index 49 Year 0 Year 1 Price /unit Quantity Value Weight (%) Price/u nit Quantity Value Weight (%) A B PP 0 1 = [(20/40)* (10/20)*.111] -1 = [ ] -1 = [.5] -1 = 2

50 50 Linkage among Value, Volume and Price Indices The change in the current price value of the indicator in our example from year 0 to year 1 can be expressed algebraically as: V t / V 0 = Σ i p i,t q i,t / Σ i p i,0 q i,0 Multiplying and dividing terms by Σ i p i,0 q i,t gives: V t / V 0 = (Σ i p i,0 q i,t / Σ i p i,0 q i,0 ) * (Σ i p i,t q i,t / Σ i p i,0 q i,t ) In terms of indices: V t / V 0 = LQ 0 t * PP 0 t / 100 (240 = 120*200/100) When V t, V 0 are known and PP 0 t is available, the Laspeyres volume index can be derived indirectly from above formula a process called price deflation

51 51 Linkage among Value, Volume and Price Indices Another set of volume and price indices may be obtained starting from the change in the current price value from year 0 to year 1: V t / V 0 = Σ i p i,t q i,t / Σ i p i,0 q i,0 Multiplying and dividing terms by Σ i p i,t q i,0 gives: V t / V 0 = (Σ i p i,t q i,0 / Σ i p i,0 q i,0 ) * (Σ i p i,t q i,t / Σ i p i,t q i,0 ) In terms of indices: V t / V 0 = LP 0 t * PQ 0 t / 100 (240 = 200*120/100) PQ 0 t can be obtained by inflating the base period values using the often available LP 0 t and then dividing the current price value by this amount

52 52 Requirements for Index Numbers Two sets of volume and price indices derived earlier: Laspeyres volume index and Paasche price index Paasche volume index and Laspeyres price index Satisfy two main requirements for volume and price measures in an accounting system: Volume measures for multiplicity of goods and services should be additive for each period The (weak) Factor Reversal Criterium that the aggregate price measure times the aggregate volume measure should be equal to the current value BUT do not satisfy two other tests: Time reversal (index for t based on 0 should be the reciprocal of that for 0 based on t) Factor reversal (product of price index and volume index =proportionate change in current values)

53 The Fisher Ideal Price Index 53 A geometric mean of the Laspeyres and the Paasche More ideal index Laspeyres has an upward bias, Paasche has a downward bias Data demanding as it requires both the Paasche & Laspeyres I 0: t Fisher = I 0: t Laspeyres I 0: t Paasche = ( I 0: t I 0: t )2 Laspeyres Paasche 1

54 Linkage among Value, Volume and 54 Price Indices Changes in values of flows at current prices can be decomposed into: Changes in their prices Changes in the volumes Therefore if prices are kept constant over time, the values are said to be in volume terms

55 Price, Quantity, Value and Volume 55 Changes in values of flows at current prices can be decomposed into: - Changes in their prices - Changes in the volumes Therefore if prices are kept constant over time, the values are said to be in volume terms

56 What is meant by Value(s) at Constant 56 Prices It is the value(s) of a product(s) for the current period using its own price(s) from an earlier period. This concept is illustrated in table below:

57 57 What is meant by Value(s) at Constant Prices Year 0 Year 1 Price Per unit Quantity Value Price Per unit Quantity Value Constant (year 0) Value (1) (2) (3) = (1)*(2) (4) (5) (6)=(4)*(5) (7)=(1)*(5) A B Tot Value increase = 1080/450 = 140% Price increase for both items = 100% Constant price increase = 540/450 = 20%

58 Estimation Methods in General 58 Three methods of deriving constant price measures Price deflation divide a current price value by a suitable price index Quantity revaluation volumes times price, may be used for current price estimates or constant price estimates Volume extrapolation extrapolate base year value by a volume index (for some people, there is only price deflation)

59 Controversy? 59 GDP at constant prices is derived as the sum of expenditure components at constant prices Expenditure components of GDP are aggregates of transactions that can be compiled by observing and recording actual transactions Value of these transactions can be factored into their own prices and quantities Therefore, better measures of price and volume for GDP conceptually may be obtained from the expenditure approach (cf. production approach) Commonly, price deflation of current values is used to derive the data at constant prices for expenditure items, although extrapolation by volume index is also used

60 Reference, Base and Weight Periods 60 Reference period (comparison period): The period in an index number time series taken as = 100 (1000) Base period (pricing period) Price base period: The period whose prices are used as denominators in calculating price relatives Pt/Po (o is the price base period) Quantity base period: The period whose quantities are used as denominators in calculating quantity relatives Qt/Qo (o is the quantity base period) Weight period: The period from which the weights are taken

61 Change of Base Year 61 Growth rate (percent) Values in current prices Pork Price Quantity Value Beef Price Quantity Value TOTAL Value

62 Change of Base Year (contd.) 62 Effects on growth rates: Growth rate (percent) Values in constant prices of 1980 Pork Beef TOTAL Values in constant prices of 1985 Pork Beef TOTAL Values in constant prices of 1990 Pork Beef TOTAL

63 63 Choice of base year in the national accounts and chaining Choice of base year? Weights need to be relevant for nearby years A normal year? (could be different from reference year) Why change base year? Structural changes in production structure examples? Structural changes in consumption patterns Structural changes in relative prices examples? Appearance of new products examples? Disappearance of old products Significant quality changes examples?

64 64 Choice of base year in the national accounts and chaining (contd.) For all these reasons, goods and services are not comparable between periods that are too far apart How far is too far five years? Same issues for price indexes as for national accounts CPI also needs to be rebased regularly and frequently What to do? Annual Chain. Even better, chain with superlative indices such as the Fisher and Törnqvist (NB rebasing base weighted series is a type of chaining, but with links equal to the number of years between base years)

65 Rebasing What is Involved? 65 Choose a base year As recent as possible With all the necessary data Often follows => HIES => CPI rebase => NA rebase Important long term planning issue (agreed at HOPS 2010) What data are needed? Current price value data at the level of detail needed Price index data (re-expressed to the NA base year) Existing constant price series up to date, along with all underlying data

66 66 Main SNA Recommendations for Price and Volume Measures: GDP and Other Aggregates Traditional Method Constant price estimates for GDP and its components, with corresponding (implicitly) Paasche price indices Change of base every 5-10 years Re-basing of whole time series Re-basing of limited period (with implicit or explicit chain-linking) State of the art Ideal method Annually chained Fischer price and volume indices for GDP and its components Calculate in a supply-use framework Second best: Annually chained Laspeyres volume indices and Paasche price indices OR Annually chained Paasche volume indices and Laspeyres Price indices

67 Fundamental Principles 67 #1 the more detail the better (for price and volume measures) #2 volume measures at the detailed level should be aggregated using Laspeyres formula, prices using Paasche formula #3 volume measures at the detailed level should be aggregated using the previous year s prices => chain volume measures (Eurostat Manual on price and volume measures in national accounts)

68 Other considerations 68 Is your CPI as good as it should be? Is coverage good enough for NA purposes? Regional coverage Product coverage e.g., telecommunications, hotels and restaurants and other tourist products... Plans for improvement Quality improvements to existing indexes? New indexes PPI, wages (especially government), export or import...? If have plans, how to develop?