OBS_VALUE: There is an explicit preference for procurements with national labour and resources content, and national suppliers are favoured to foreign suppliers with a price-margin preference up to 15% over the price offered by foreign tenders. Moreover, public tenders are open to international bidders only when a) the national tender has been declared void (because of lack of valid national tenders), and b) it is a specific condition of the procurement financed by external credit granted to México. Tenders under the Public Work Law are only open to foreigners on the base of reciprocity.