f2ad9ac4ffc51a27175f2043c16eed09.ppt

- Количество слайдов: 21

Regional Data Validation Expert Group Meeting on Price Statistics and National Accounts: ICP Round 2011 Jointly organized by: UN-ECLAC, CARICOM, CARTAC and ECCB 27 th-30 th August 2012 Aruba

Summary INTRA country data validation INTER country data validation Quaranta Tables Dikanov Tables Case Study

Data validation procedure The data validation procedure has two main steps: INTRA country validation INTER country validation Countries and ECLAC participate in this procedure It is an iterative process

Step 2: INTER country validation The main data analysis within inter-country and global validation is carried out by using two validation tables that are • The Quaranta Tables • The Dikhanov Tables The purpose of the both tables is to • Screen the national average prices for possible errors by comparing the average prices for the same product in different countries • Possible errors are highlighted by special indices This analysis can lead to • Editing of price data for an item • Editing of metadata for an item

Quanranta Tables validation tables The Quaranta Tables (QTs) consist of a set of tables • Table details • Summary tables for each BH • Individual tables for each item QTs can be used for the validation of • BH PPPs and PLIs • Item XR-ratios and PPP-ratios Different calculation options • EKS, EKS*, CPD, CPRD and W-CPD • Recommended method by the TAG is weighted CPD • However comparison of results for different calculation methods can be used to value given information on importance

QUARANTA TABLE DIAGNOSTICS - Rice Data Selection Criteria Basic Heading Code 99. 11. 01. 1 Averaging Method Arithmetic Mean Run Date Time Period Yearly Imputation CPD Summary Information No of Items included in the Average weight of Basic Analysis 6 out of 6 Heading in Total Expenditure No of Countries included in the Analysis 18 out of 18 Average Coefficient Variation Base Country Table details 4/13/2011 0. 0 27. 4 USA Country Level Details BH table # Shares are multiplied by 10000. Country XR PPP PLI(%) Weight # Items Var. Country 1 4. 42 1. 8150 41. 080% 0. 0 2; *0 7. 2 Counrty 2 959. 04 718. 2770 74. 896% 0. 0 5; *0 8. 2 Counrty 3 1018. 35 2. 7696 0. 272% 0. 0 2; *0 33. 8 Item Level Details 99. 11. 01 Country Long grain rice, prepacked Quotati NC-Price ons Var. Co. XR-pr Var. Co. : PPPXR-ratio price 25. 9 1 -Kilograms PPPratio Pref. Uo. M Country 1 1. 500 151 11. 2 0. 34 45. 89 0. 83 95. 02 NA Country 2 - - - - NA Country 3 766. 381 10 3. 0 72. 93 9857. 61 1. 14 130. 66 NA Item table

Table details Quaranta tables # Basic Heading Code Period during which the prices for the products covered by the Table were Period collected. Run date for the tables Averaging Method used to calculate the averages Method Imputation Method used to calculate the basic heading PPPs EKS, EKS*, CPD or CPDR. # Number of Items included in the analysis National expenditure weights scaled to 100, 000. That part of a country's GDP that is spent on the basic heading when both expenditures are expressed in Weight national currency and valued at national price levels. For information only: not used in the calculations # Number of Countries included in the analysis Overall variation coefficient i. e. the average product variation coefficient for Average the products priced for the basic heading. It is calculated as the unweighted Coefficient arithmetic mean of the product variation coefficients at. It measures the Variation average variation of the PPP-Ratios of all products priced for the basic heading. Base Country Base country for the calculations (currency selected as numéraire).

BH Table details Quaranta tables BH table details Country XR PPP PLI Weight No. of Items Var. Co. Names of countries covered by the Table. Market exchange rates of the countries expressed as the number of units of national currency per unit of the numéraire currency (base country). Purchasing power parities for the basic heading calculated and expressed as the number of units of national currency per unit of the selected numéraire currency. The prices used to calculate the PPPs are the average prices in national currencies that countries report for the products they priced for the basic heading - that is, the NC-Prices. Price Level Indices. The PPPs expressed as a percentage of the corresponding exchange rate. National expenditure weights scaled to 100, 000. That part of a country's GDP that is spent on the basic heading when both expenditures are expressed in national currency and valued at national price levels. Number of products that are priced by each country for the basis heading and the number of products priced by each country that are important - that is, the number of products assigned an asterisk (*). Country variation coefficient. The standard deviation of the country's CUP-Ratios for all products priced by the country for the basic heading expressed as a percentage of the arithmetic mean of the country's CUP-Ratios for all products priced by the country for the basic heading.

Item table details Quaranta tables Item table details Code Var. Co. Code, name, and summary definition of the product covered in the subsequent product section. Item variation coefficient. The standard deviation of the product's PPP-Ratios expressed as a percentage of the arithmetic mean of the product's PPP-Ratios. Pref. Uo. M Unit of measurement Country name NC-Price Average price in national currency (NC). Quotations Number of price observations on which the average prices in national currency are based. Var. Co. XR-Price XR-Ratio Price observation variation coefficient. The standard deviation of the price observations underlying the product's average price expressed as a percentage of the arithmetic mean of the price observations underlying the product's average price. The average prices in national currency in column [24] converted to the numéraire currency with the exchange rates. Standardized price ratios based on the exchange rate converted prices. The XR-Prices expressed as a percentage of their geometric mean. PPP-Price The average prices in national currency converted to the numéraire currency with the PPPs. PPP-Ratio Standardized price ratios based on the PPP converted prices. The PPP-Prices expressed as a percentage of their geometric mean. Geo Mean Geometric mean of the exchange rate converted prices and CUP-Prices

PPP Price: It is the national average price for a specific product of a specific country deflated by PPP. This price indicates how many units of currency of the base country are needed to buy the same quantity of a specific product that are bought with one unit of currency of the base country in the base country. Since PPP are calculated based on all the products that made up the BH, the PPP price indicates how a product behaves in a specific country with respect to other products in the same country.

PPP ratio is the PPP price divided by the geometric mean of PPP prices in all the countries. The value of this ratio indicates how the country behaves in comparison with other countries for a specific product. That is to say, how the price behaves relative to the other products of the country in the BH and relative to the rest of the countries for the same product. The average of all the PPP ratios for a specific country is 1 (or 100%) inside a BH, and at the same time, the average of PPP ratios for all the countries for a specific product is 100%

Suggested critical values: CV larger than 33% Ratios outside (80% - 125%) range. With this tool one can detect problems with the quality of data such as: High price variation for a certain product in each country. Average prices which are too high (or low) in nominal terms compared to the price in other countries when converted with exchange rate. Average prices which are too high (or low) in real terms compared to the price in other countries when converted with PPP Behavior of average prices inside a BH. For instance when the prices for the majority of the products in a specific BH for a specific country are below (above) the regional average and for a certain product the price is above (below) regional average.

Dikhanov Tables validation tables As the QTs, the Dikhanov Tables (DTs) consist of a set of tables • Table details • Summary table for each BH • Individual tables or rows for each item DTs can be used for the validation of • Aggregated (above BH) and BH PPPs and PLIs • Item XR-Ratios and CPD(R) residuals Different lay-out options including color scheme • Aggregate/BH tables + full item statistics • Aggregate of BH tables + simple residual rows for item Different calculation options • CPD, CPRD, CPD-W

DT can be used as a substitute or complement of QT in order to detect potential problems with the data. QT analyse one BH at a time. For certain products it is difficult to detect outliers with QT (biased averages due to lack of countries collecting data for a specific product) The main difference between QT and DT is that the analysis in DT does not consider data grouped by BH but it considers them individually and simultaneously. This makes easier the analyses for those products which are the only representative of a BH or when there a few products in a BH.

Overview Dikhanov tables Dikhanov Temporal Analysis PPP STD No. of Priced Items ER (LCU/US$) Rebased_XR PLI Country 1 Yearly - 2005 2. 934690064 0. 245237431 420 2. 43 4. 41818 0. 664230261 Country 2 Yearly - 2005 658. 1289976 0. 256006128 513 527. 47 959. 0363636 0. 686239878 Item Level Details Item Code Item Name 99. 11. 01. 1 Rice PPP STD PLI No. of Priced Items 99. 11. 01. 11. Long grain rice, prepacked 1. 01 Average Price No. of Observations Coefficient of Variation XR Ratio Country 3 Yearly - 2005 4. 040426119 0. 291549487 572 5. 78 10. 50909091 0. 384469613 Table details Country 1 Country 2 Country 3 Yearly - 2005 1. 81507 0. 05109 0. 410819 2 718. 297 0. 0726994 0. 748978 5 4. 84856 0. 274263 0. 461368 6 -0. 05109 1. 5 151 11. 2214 70. 4386 - 0. 26746 5. 51 10 3 108. 78 BH table Item table

Table details Dikhanov tables Table Details PPP Purchasing power parities for the basic heading or aggregate covered by the Table. They are expressed as the number of local currency units per unit of the selected numéraire currency. The prices used to calculate the PPPs are the average prices in local currencies that countries report for the products they priced for the basic heading or aggregate - that is the average prices. STD Standard deviation of each country’s CPD or CPRD residuals for the basic heading or aggregate. It can be converted to a country variation coefficient by multiplying by 100. # Number of products specified for the basic heading or aggregate. ER Market exchange rates of countries expressed as the number of local currency (LCU/US$) units per US dollar. Rebased XR Exchange rates rebased to the numéraire currency. Number of local currency units per unit of numéraire currency. PLI Price level indices. The PPPs expressed as a ratio of the corresponding rebased exchange rates in row.

BH details Dikhanov tables BH Details Item code Code of the basic heading or aggregate covered by the Table. Item name Name of the basic heading or aggregate covered by the Table. Period during which the prices for the products covered by the Table were Period collected. PPP Purchasing power parities for the basic heading or aggregate covered by the Table. They are expressed as the number of local currency units per unit of the selected numéraire currency. The prices used to calculate the PPPs are the average prices in local currencies that countries report for the products they priced for the basic heading or aggregate - that is the average prices. STD Standard deviation of each country’s CPD or CPRD residuals for the basic heading or aggregate. It can be converted to a country variation coefficient by multiplying by 100. PLI # Price level indices. The PPPs expressed as a ratio of the corresponding rebased exchange rates in row. Number of products specified for the basic heading or aggregate.

Item details Dikhanov tables Item Details Item code Code of the basic heading or aggregate covered by the Table. Item name Name of the basic heading or aggregate covered by the Table. Period STD Count Residual Period during which the prices for the products covered by the Table were collected. Standard deviation of the product’s CPD or CPRD residuals. It can be converted to a product variation coefficient by multiplying by 100. The mean of a product’s residuals is 1. Number of countries pricing the product. CPD or CPRD residuals by product and country. CPD residuals in the Dikhanov table are equal to the logarithms of the CUP-Ratios in the Quaranta table. Average Price. Average price in local currency units. # Number of price observations on which the average prices at [16] are based. Coef. of Var. Price observation variation coefficient. XR Ratio Price ratios based on exchange rate converted prices. The converted prices expressed as a percentage of their geometric mean.

Relation between Quaranta and Dikhanov Tables Both tables provides essentially the same information, but • Dikhanov Tables can be compiled for a group of BHs (an aggregate), they use color schemes to highlight potential outliers and can be collapsed to present only residuals for items • Quaranta tables presents the relations within an item potentially clearer Relation between PPP-Ratios and CPD residuals • CPD residuals are equal to the logarithms of CUP-ratios PPP-Ratios 0 to 14 14 to 47 47 to 78 78 to 128 Less than -2. 0 to 0. 75 -0. 75 to 0. 25 -0. 25 to 0. 25 CPD residuals 128 to 212 to 739 0. 25 to 0. 75 to 2. 0 739 to More than 2. 0

Case Study We will analyze a Quaranta Table and highlight the problems encountered. We will follow the instructions provided in this presentation.

THANK YOU 21