Abstract
The problem of balancing economic accounts has been recognized for a long time. In 1942, Richard Stone et al. proposed a weighted least squares approach (hereafter SCM approach) to balance small economic accounts. This approach has been extended to accommodate reconciliation of large-scale national accounts (NA) systems. The main challenge turned out to be the estimates of the uncertainties of initial NA aggregates. In this study, we try the SCM approach for automatically balancing a large-scale supply-use framework in the Swedish NA. Efforts are made to estimate the uncertainties not only from sampling errors but also from non-sampling errors. The error estimates are used as weights in the balancing procedure. The approach is evaluated through a test run in parallel with a real compilation of the Swedish annual NA. Our study shows that the automatic balancing procedure is feasible to implement in the production environment of Statistics Sweden. Compared with the current mainly manual balancing process, the automatic procedure is faster, cheaper and requires less time from the NA experts. Above all, the method is transparent and new information can easily be accounted for.
Introduction
The uncertainty associated with the national accounts (NA), such as the gross domestic product (GDP), is of great interest for decision-makers, researchers, and the public. This information is nevertheless often absent in statistical releases. This is partly due to the complexity of the compilation of NA that uses a large number of data sources. It is difficult to estimate all uncertainties of the initial estimates. In a report [1], the data sources and possible error sources of NA compilation are well documented. The difficulties related to identifying and quantifying the errors, and in particular, the non-sampling errors are discussed. In paragraph 52 of report [1], it is stated, “given the current state of the art, it is not possible to calculate objective error margins for national accounts aggregates.”
Furthermore, NA must comply with the restrictions of accounting systems. There are three approaches for calculating GDP in the NA: the expenditure, the production, and the income approach. Usually, the estimates of these different approaches differ. It is therefore necessary to have a post-adjustment (“balance”) of those estimates. The balancing is usually done within the supply-use framework, i.e., the supply and use of different products CPA (Classification of Products by Activity). The balancing process is important for the compilation of NA. However, this process is not only highly demanding of expertise and time, but it is also to a large extent manual, which further complicates eventual attempts to investigate the uncertainties of the balanced NA aggregates.
In 1942, Richard Stone and others ([2], hereafter SCM) proposed a weighted least square (WLS) approach to balance economic accounts on a limited scale. Other authors, in particular [3, 4], formalized the approach and associated it to a Lagrange Multiplier approach with a quadratic loss function. A few applications [5, 6, 7, 8, 9, 10] have been reported. Among others [7, 8] used the SCM application to reconcile the US Industry Accounts and distribute the aggregate statistical discrepancy to industries in the Bureau of Economic Analysis (BEA). These articles show that the method is feasible and empirically efficient, although it is still difficult to obtain objective estimates to the uncertainties.
In our work, an SCM balancing approach is investigated within a supply-use (SU) framework in the Swedish NA; the income approach has not implemented completely in Sweden. The aim is to construct a framework workable in the real production environment of the NA compilation and balance. Efforts have been made to estimate the uncertainties from not only the sampling errors but also non-sampling errors. Those estimates are used then as weights in the balancing procedure. In Section 2, the framework of generalized least squares and a flexible equivalent optimization setting are described. The estimation of uncertainties of initial NA estimates is presented in Section 3. The Swedish application of this approach, along with the results, is given in Section 4. Discussion of the results, other related and future work are given in Section 5.
The framework
Following the description in [3, 8], write the estimates in NA as a vector
Furthermore, under the condition that
Note that the vector
In practice, following [3, 7], a more workable formula under the SU framework is used in our study. Consider the following notation. For
The corresponding initial estimates are indicated with a superscript 0 and
over
The constraints of Eq. (2) include that for each industry
Similar restrictions apply to the intermediate consumption, the domestic final uses, export and import, respectively:
The NA accounting requires further that the total supply is equal to the total use for each product
Note that compared with the theoretical framework Eqs (1) and (2), it is assumed implicitly that there is no covariance in
It is worth noting that Eqs (2)–(2) is a standard convex optimization problem and that a solution exists and is unique (see e.g. [11]).
Previous studies on the balancing of NA, in particular SU or Input-Output tables, such as [12] have not made use of the uncertainties of the initial estimates. In the BEA application of the US [7, 8], the SCM approach is carried out for the reconciliation and redistribution of the statistical discrepancy after a general revision of the NA estimates. In this application, the expenditure-based estimates are considered final and are not changed. Our settings aim nevertheless to create a framework workable in the real production environment of the NA compilation and balancing.
Efforts are also made in our study to estimate the uncertainties of the initial estimates
See Section 3 for a description of the last two alternatives.
The sampling errors
As previously mentioned, it is a huge challenge to estimate the uncertainties of
Recall that in our application where
It is seldom in the NA compilation that the basis of NA figures (e.g.
In Eq. (9) the summation is over all the non-sampling error sources.
Table 1 (Row SE) below shows our estimate of the uncertainties,
The estimate of sampling uncertainties (SE) and total uncertainties (TU) in the output in different CPA product groups from the NACE industry G46 (percentage)
The estimate of sampling uncertainties (SE) and total uncertainties (TU) in the output in different CPA product groups from the NACE industry G46 (percentage)
It can be seen that there are quite big differences between the sampling uncertainties in different CPA product groups. These vary from CPA G45T47 (Industries for Wholesale and retail trade and repair services, 1.0 percent) to CPA N80T82 (Security and investigation services; services to buildings and landscape; office administrative, office support and other business support services) which is very difficult for survey sampling with a sampling error of 29.1 percent. It is this information that we try to take advantage of in the SCM balancing approach. Some product groups have zero in their uncertainty estimates, which means that the NACE industry cannot produce those products. Such items will be omitted from the optimization expression of Eq. (2) and instead kept unaltered. Recall that the total outputs from NACE G46 (
Analogously the total uncertainties
All the necessary estimates of the uncertainties in
The initial estimates
The SCM balancing approach was tested under an SU framework parallel with the real compilation of Swedish Annual NA 2014 during April–June 2016 at Statistics Sweden. The existing balancing process is carried out for 400 product groups. The first stage consists of manual balancing and lasts for about two months. The second stage consists of a final, mechanical balancing using the RAS method [15] mainly applied to intermediate consumption. In our application, there are 66 industries (
Basic information for the application of SCM balancing approach to the Swedish Annual NA
Basic information for the application of SCM balancing approach to the Swedish Annual NA
Mathematical Programming Package SAS/OR
Table 3 shows the adjustments by the SCM balancing approach with different weights in Test Round 3 and the actual balancing, summarized to NA aggregates in the use side Intermediate consumption (IC), Household final consumption expenditure (HFCE), Government spending (G), Gross fixed capital formation (GFCF), Changes in inventories (CI), and Exports; and in the supply side Gross value of output (GVO), Imports, and Taxes (taxes minus subsidies).
Adjustments (MSEK) of the NA aggregates by the SCM approach with different weights CW, NW, SE, and TU in Test Round 3, and the actual balancing
Adjustments (MSEK) of the NA aggregates by the SCM approach with different weights CW, NW, SE, and TU in Test Round 3, and the actual balancing
It is known that the WLS with constant weights reduce to the ordinary least squares and that all input variables will have approximately equal adjustments regardless of their magnitude; whilst with neutral weights, they will have adjustments approximately proportional to the squares of their magnitude (Columns CW and NW in Table 3). It can also be seen that in the late stage of the actual balancing procedure, basically the adjustments are made only to the Intermediate consumption and Gross value of output, which are considered to be unreliable, based on experience and convention in the NA department at Statistics Sweden. However, it is natural and sensible that the more unreliable the initial NA estimates are, the more they should be adjusted. A close examination of the uncertainties that we estimated (not reported) shows that although the estimates of the Intermediate consumption by CPA product groups are highly uncertain, the IC totals by industries are rather reliable: this implies that the IC should not be adjusted too much. At the same time, there are high uncertainties in the estimates of HFCE and Exports (in particular of services), GFCF (in particular in manufacturing), and CI. Bigger adjustments to these estimates in the balancing may be motivated. Note that in Test Round 2, the actual balancing approach makes instead less adjustment to HFCE, CI and Exports (Table 4) than the SCM approach.
Adjustments (MSEK) of the NA aggregates by the SCM approach with TU in Test Round 2, and the actual balancing
It should be noted that GDP is in fact not an aggregate compiled directly in NA, but derived from the balanced SU tables. Different balancing approaches lead consequently to different GDP estimates. The Swedish annual GDP estimate (excluding non-market products) derived from the SCM approach and the actual balancing are shown in Table 5. Observe that there is no true value for the GDP estimate and the estimates in Table 5 cannot be used directly to evaluate the balancing approaches. However seems after all too early to apply the automatic balancing at the time of Test Round 1, while those of Test Rounds 2 and 3 might be appropriate.
The estimates of Swedish annual GDP (MSEK, excluding non-market products) from the SCM approach with TU in different test rounds and the actual balancing
Estimation of the uncertainties and balancing the double entities of NA estimates are known difficult problems in national statistical institutes (NSI). The SCM approach that we generalized from [2] is investigated in our study. It is shown that an automatic balancing approach is possible for the compilation of NA in NSI. With the SCM approach, the balancing is not only more objective, but also fully replicable. Furthermore, the manual balancing procedure existing today requires much more resources and expertise. However, in order to implement the SCM approach in the official statistics production, more experiments have to be carried out and evaluated since there is no obvious evaluation criterion to compare with the manual procedure.
It is a big challenge to estimate the uncertainties in the initial NA estimates. There is little work available in the literature concerning the quantification of the non-sampling errors and how to combine them with the sampling errors. In our study, the sampling errors are used as the basis and a direct expert judgment is done for the non-sampling errors. This approach may be arguable. It is nevertheless a first step to tackle this difficult problem. Recently [16] proposed, instead to handle the variance-covariance matrix for individual input variables, to consider accounting equations as single entities and developed scalar uncertainties measures for those entities. They showed appealing theoretical properties of this approach. It would be of great interest to follow applications of this approach in the NA.
The balancing investigated in our study is only for one period. It is possible to use this approach for multiple-year balancing; see [17] for such an application, where the balanced result satisfies not only the accounting constraints, but also show movements that are as close as possible to the preliminary information. Moreover, in a broader context of balancing, not only accounting constraints, but also temporal constraints (i.e. the sum of quarterly accounts in a year equal to the annual ones) have to be satisfied in systems of time series. Readers who are interested in this area are referred to [18] for approaches for a reconciliation of both accounting and temporal constraints, and to the monograph [19] by Dagum and Cholette for general reconciliation methods.
Our application is done on the current prices. It is not trivial to extend the approach to the constant prices. The possibility to compute the uncertainty of the balanced aggregates, such as GDP, and the theoretical property Eq. (2) are of great interest. However, the conditions are very difficult to verify. All those are possible topics for our future work.
Footnotes
Acknowledgments
The authors are very grateful to the associate editor and three anonymous referees for their comments and suggestions, which have greatly improved the readability of the paper. The contribution of our colleagues to this study is acknowledged, in particular, the efforts to make the uncertainty estimates available. The study has been presented at several seminars and conferences. The authors thank the participants for helpful discussions and suggestions.
