Expert Group Meeting on Price Statistics and National Accounts:

ICP Round 2011 

Jointly organized by:UN-ECLAC, CARICOM, CARTAC and ECCB

27th-30th August 2012Aruba

SummaryINTRA country data validation INTER country data validation

Quaranta TablesDikanov Tables

Case Study

Data validation procedureThe data validation procedure has two main

steps:INTRA country validationINTER country validation

Countries and ECLAC participate in this procedure

It is an iterative process

• The Quaranta Tables

The main data analysis within inter-country and global validation is carried out by using two validation tables that are

• Screen the national average prices for possible errors by comparing the average prices for the same product in different countries

The purpose of the both tables is to

Step 2: INTER country validation

• The Dikhanov Tables

• Editing of price data for an item

This analysis can lead to

• Editing of metadata for an item

• Possible errors are highlighted by special indices

• Summary tables for each BH

The Quaranta Tables (QTs) consist of a set of tables

• BH PPPs and PLIs

QTs can be used for the validation of

Quanranta Tablesvalidation tables

• Individual tables for each item

• EKS, EKS*, CPD, CPRD and W-CPD

Different calculation options

• Recommended method by the TAG is weighted CPD

• Item XR-ratios and PPP-ratios

• However comparison of results for different calculation methods can be used to value given information on importance

• Table details

QUARANTA TABLE DIAGNOSTICS - Rice

Data Selection Criteria

Basic Heading Code 99.11.01.11.1 Time Period Yearly

Run Date 4/13/2011

Averaging Method Arithmetic Mean Imputation CPD  

Summary InformationNo of Items included in the Analysis 6 out of 6

Average weight of Basic Heading in Total Expenditure 0.0  

No of Countries included in the Analysis 18 out of 18 Average Coefficient Variation 27.4  

Base Country USA  

Country Level Details

# Shares are multiplied by 10000.  

  Country XR PPP PLI(%) Weight # Items Var.Co.  

  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

99.11.01.11.1.01 Long grain rice, prepacked

Var.Co.: 25.9 1-Kilograms

Country NC-PriceQuotati

ons Var.Co. XR-pr XR-ratioPPP-price

PPP-ratio Pref. UoM

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

Table details

BH table

Item table

Table detailsQuaranta tables

# Basic Heading Code

Period Period during which the prices for the products covered by the Table were collected.

Run date Run date for the tablesAveraging Method Method used to calculate the averages

Imputation Method used to calculate the basic heading PPPs EKS, EKS*, CPD or CPDR.# Number of Items included in the analysis

Weight

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. For information only: not used in the calculations

# Number of Countries included in the analysis

Average Coefficient Variation

Overall variation coefficient i.e. the average product variation coefficient for the products priced for the basic heading. It is calculated as the unweighted arithmetic mean of the product variation coefficients at. It measures the average variation of the PPP-Ratios of all products priced for the basic heading.

Base CountryBase country for the calculations (currency selected as numéraire).

BH table detailsCountry Names of countries covered by the Table.

XR Market exchange rates of the countries expressed as the number of units of national currency per unit of the numéraire currency (base country).

PPP

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.

PLI Price Level Indices. The PPPs expressed as a percentage of the corresponding exchange rate.

WeightNational 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.

No. of ItemsNumber 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 (*).

Var.Co.

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.

BH Table detailsQuaranta tables

Item table detailsQuaranta tables

Item table detailsCode Code, name, and summary definition of the product covered in the subsequent product section.

Var.Co. 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. UoM Unit of measurement Country Country nameNC-Price Average price in national currency (NC).

Quotations Number of price observations on which the average prices in national currency are based.

Var.Co.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.

XR-Price The average prices in national currency in column [24] converted to the numéraire currency with the exchange rates.

XR-Ratio 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.

• Summary table for each BH

As the QTs, the Dikhanov Tables (DTs) consist of a set of tables

• Aggregated (above BH) and BH PPPs and PLIs

DTs can be used for the validation of

Dikhanov Tablesvalidation tables

• Individual tables or rows for each item

• CPD, CPRD, CPD-W

Different calculation options

• Item XR-Ratios and CPD(R) residuals

• Table details

• Aggregate/BH tables + full item statistics

Different lay-out options including color scheme

• Aggregate of BH tables + simple residual rows for item

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 are a few products in a BH.

OverviewDikhanov tables

Table details

BH table

Item table

Dikhanov Temporal Analysis Country1 Country2 Country3

Yearly - 2005 Yearly - 2005 Yearly - 2005 PPP 2.934690064 658.1289976 4.040426119 STD 0.245237431 0.256006128 0.291549487 No.of Priced Items 420 513 572 ER (LCU/US$) 2.43 527.47 5.78 Rebased_XR 4.418181818 959.0363636 10.50909091 PLI 0.664230261 0.686239878 0.384469613   

Item Level Details Country1 Country2 Country3Item Code Item Name Yearly - 2005 Yearly - 2005 Yearly - 2005

99.11.01.11.1 Rice  

PPP 1.81507 718.297 4.84856 STD 0.05109 0.0726994 0.274263 PLI 0.410819 0.748978 0.461368 No.of Priced Items 2 5 6

99.11.01.11.1.01 Long grain rice, prepacked -0.05109 - 0.26746

Average Price 1.5 - 5.51 No.of Observations 151 - 10 Coefficient of Variation 11.2214 - 3 XR Ratio 70.4386 - 108.78

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.

STDStandard 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 (LCU/US$)

Market exchange rates of countries expressed as the number of local currency 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.

Table details Dikhanov tables

BH detailsDikhanov tables

BH DetailsItem 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 Period during which the prices for the products covered by the Table were 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.

STDStandard 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 detailsDikhanov tables

Item DetailsItem 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 Period during which the prices for the products covered by the Table were collected.

STDStandard 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.

Count Number of countries pricing the product.

Residual 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 PriceAverage 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.

Both tables provides essentially the same information, but

• CPD residuals are equal to the logarithms of CUP-ratios

Relation between PPP-Ratios and CPD residuals

Relation betweenQuaranta and Dikhanov Tables

• 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

0 to 14 14 to 47 47 to 78 78 to 128 128 to 212 212 to 739 739 to

Less than -2.0

-2.0 to -0.75

-0.75 to -0.25

-0.25 to 0.25

0.25 to 0.75 0.75 to 2.0 More

than 2.0

CPD residuals

PPP-Ratios

Case StudyWe will analyze a Quaranta Table and

highlight the problems encountered.We will follow the instructions provided in

this presentation.

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