in the production of Development Plans under the Planning Act, one of the most essential basic facts which must be established is the proper amount of land which should be zoned for industrial use. This is particularly important in built-up areas where building land is scarce, but even in rural areas it is very undesirable either to zone too much land for industry, which tends to produce a scattered type of development which is untidy and costly in roads, or to zone too little land which tends to produce local unemployment or needlessly long journeys to work.