Each year, an official estimate of the stock of cod in the Grand Banks is announced  This estimate is obtained by averaging two separate estimates of how many cod are available, one based on the number of cod caught by research vessels during a once-yearly sampling of the area and the other on the average number of tons of cod caught by various commercial vessels per unit of fishing effort expended there in the past year -- a unit of fishing effort being one kilometer of net set out in the water for one hour  In previous decades, the two estimates usually agreed closely
However, for the last decade the estimate based on commercial tonnage has been increasing markedly, by about the same amount as the samplingbased estimate has been decreasing
Last year's official estimate was probably not much different from the official estimate ten years ago.