impediment of collecting reliable data<sup>8</sup> and constructing comprehensive indicators on standards in different sectors across countries. Among the papers that have found evidence as to the negative effects of standards on trade from African countries, Otsuki et al. (2001) examine the impact of European aflatoxin standards on African groundnut exports. They find that a 10 percent increase in restrictiveness is associated with a fall in trade volume of about 11 percent. Disdier et al. (2007) use data on WTO notifications of mandatory sanitary and phyto-sanitary measures, as well as technical regulations, to measure the impact of standards across a large number of sectors. They generally find that standards are associated with negative trade impacts, in particular for exports from developing countries to OECD countries.

On the positive net impact of standards on trade, Moenius (2004) observes that countryspecific standards tend to promote trade in the manufacturing sector. However, the opposite result holds for homogeneous goods, such as agricultural products. Such an outcome could be consistent with the interpretation that higher information costs in manufactures can be surmounted by standards.

One way to reduce the costs associated with standards is through international harmonization of standards. This can limit the need for exporters to alter products to meet multiple standards for different markets. Czubala, Shepherd, and Wilson (2007) examine the impact of EU standards on African textiles and clothing exports. By identifying standards aligned with ISO (International Organization for Standardization) standards (as a proxy for de facto international norms), the authors find evidence that non-harmonized standards reduce African exports. In contrast, they find that EU standards harmonized to ISO standards are less trade restricting. Their results suggest that efforts to promote African exports of manufactures may need to be complemented by measures to reduce the cost of product standards through new efforts to support international harmonization of standards. The authors suggest that steps to harmonize national standards with international norms, including through the World Trade Organization’s Technical Barriers to Trade Agreement, promise concrete benefits for African exporters.

> 8 Although it is difficult to directly observe the possible trade benefits of standards, we do know something more about their direct cost impacts. The World Bank Technical Barriers to Trade database (Wilson and Otsuki, 2004) provides some informative data. In Sub-Saharan Africa, firms invest on average 7.65 percent of sales in order to comply with foreign standards. These data also show, however, that experiences differ greatly from one firm to another: the range of investment costs reported by firms runs from 0.01 percent of annual sales to 124 percent. Part of this apparent variation is due to the metric used: for constant costs, larger companies with higher levels of sales will tend to report lower costs as a percentage of sales. It also suggests that firms may have some leeway in terms of how they react commercially to changes in foreign standards.

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