The performance of an economy reflects the interaction of many economic variables and underlying relationships. The main economic relationships examined may be summarised as follows:
Domestic expenditure. Projections of private consumption typically take into account real disposable income, household wealth, changes in the rate of inflation, monetary and financial conditions, and leading indicators of consumer confidence and retail sales. Business fixed investment is mainly assessed in relation to non-financial indicators (sales, output and capacity utilisation) and financial variables (cash flow and interest rates). Business survey information is also taken into account. Projections for residential construction take account of demographic trends, housing stocks, real income and financial conditions, and also draw on cyclical indicators for the construction sector. Projections of stockbuilding are usually made with reference to relevant stock-output and stock-sales ratios.
Employment, wages and prices. Employment and other labour market trends are generally assessed on the basis of actual and projected output. Important additional elements relate to productivity trends, capacity constraints and costs. Unemployment rate projections are derived from employment and labour supply projections, with the latter assessed on the basis of demographic trends and participation rate assumptions. Wage and earnings assessments take into account a number of key factors, such as the pattern of current wage settlements data as a leading indicator. Labour market demand pressures, productivity developments and the terms of trade also influence the overall projection for real wages and real compensation per employee. The assessment of domestic prices and inflation trends depends crucially on unit costs, the strength of demand output gaps and foreign prices.
Output gaps. The output gap is measured as the difference between actual and estimated potential GDP, in volume terms and in per cent of potential GDP. Output gaps are difficult to estimate and subject to substantial margins of error, since the concept of constant prices is odd now that chain-linking is becoming the norm. Potential output is based on a production function approach, taking into account the capital stock, changes in labour supply, factor productivities and underlying "non-accelerating inflation rates of unemployment" (NAIRU) for each Member country.
Foreign trade and balance of payments. As noted on several instances, particular attention is given to ensuring the consistency of international trade volume and price projections, since trade represents a principal channel through which developments in one country affect other economies. The initial projections for aggregated import volumes of goods and services are derived from activity (expenditure) and lagged competitiveness positions. Aggregate goods and services export volume projections are based on developments in export markets and competitiveness positions. Projections for export prices (the deflator for goods and services exports as measured on a national account basis) are based initially on movements in unit labour costs, import prices, and competitors' export prices while import prices are derived as weighted averages of foreign costs and domestic prices. Investment income receipts and payments reflect returns on stocks of external assets and liabilities.