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The criteria for carrying out the A-B-M approach are as follows:

- 1) Matching starts with the commodities which are relatively most important with regard to their value of output'.

- 2) A product wi-_ be matched only if the description of the commodity in both censuses is more or less consistent.

- 3) It is preferable Ko match "homogeneous" products such as passenger vehicles of a specific weight and engine size rather than a "heterogeneous" product s .ch as "passenger vehicles". However, if the item specified in the census of one country is rather heterogeneous, while it is divided up into separate homogeneous products in the census of the other country, we mty be forced to combine the latter country' s homogeneous items into a single heterogeneous product in order to achieve a match.

- 4) Although we only attempted to find a match for items which account for more than 1 per cent of the total value of output of the industry in either country, in some cases small items are included in the matching procedure. Two cases exist when this may occur: - When carrying out a match between two important items in both countries, it may be necessary to include some smaller items, in order to get a proper match. For example, it can be seen from table 5.3 that matching Mexican "Trucks" and "Truck Cab Chassis" (contributing respectively 15.36 and 3.27 per cent to the total value of output) with US trucks, implies inclusion of five small Mexican product items which also refer to trucks;

- An important product item which contributes more than 1 per cent to the total value of output of the industry in one country may be matched with a less important item in the other country. An example derived from table 5.3 is Mexican "Passenger Truck Bodies" (contributing 1.21 per cent to the total value of output) which are matched with US "Utility Trucks", which contribute only 0.07 per cent to the total value of output in the US.

- 5) The matching procedure is continued until we come to deal with items which contribute less than 1 per cent to the total value of output in both countries. This 1 per cent "cut off" level was determined by empirical testing for some of the sample industries. Higher cut-off levels, for example 5 per cent, would bring down sample coverage too much, and therefore lead to an unacceptable loss of product information.

The advantage of using a systematic matching procedure is important, when one has to deal with:

- a large industry with many product items, for example, textiles or footwear and leatherware, and/or

- a technically complicated industry producing items difficult for an inexperienced researcher to characterize, for example, motor vehicles and equipment and iron and steel.

Systematic application of the A-B-M method provides researchers, who are not experienced in this field, with a reliable technique for making relevant international price comparisons which involves a minimum element of ad hoc judgment. Moreover, the method is time-saving. The execution of' a

- l For all industries Al to A17 (see Statistical Appendix) we show summary tables for each matching procedure, which ranks the items according to their value of output, and which shows if they are matched are not and how much they contribute to the cumulative matching percentage.