In 1273, he created the Mesta, an association of some 3,000 petty and great sheep holders in Castile, in reaction to less wool being exported from the traditional sites in England. This organization later became exceedingly powerful in the country (as wool became Castile's first major exportable commodity and reported a trade surplus, called "white gold", as the wool amount was critical to the health of the population during the winter), and eventually its privileges were to prove a deadly wound in the Castilian economy. One side effect of the quickly expanding sheep herds was the decimation to the Castilian farmland through which the sheep grazed.