In Finland the amount of forests between ages of 20 to 80 was 10.8 million hectares in 1990-1991 which was 51% of forest land area. According to the thinning models of central forestry administration (Forestry Center Tapio), there were 6.9 million hectares (33% of forest land area) to be thinned immediately if there was no minimum per hectare harvest limit. One third of this area is in the stage of the first thinning. If there was a 20 Kubikmeter/ha minimum harvest limit the amount of thinning forests decreased to 4.4 million hectares (21% of forest land area). The amount of thinning forests has strongly increased during the history of national forest inventories though the amount of forests at the thinning age has not essentially changed. So the forests at the thinning age are at present more dense than before according to the inventory results. The profitability calculations showed that neglecting thinnings resulted in 40 years in a loss of 150-200 milliard marks of future revenues at the end of the planning period (net present value in 2030). Futher, the volume of saw timber would be 700 million Kubikmeter smaller than by using the thinning models of Tapio. The total volume increased even without thinnings up to 2.1 milliard Kubikmeter by the year 2030 though this was over 500 million Kubikmeter smaller than when carrying out the models of Tapio. Thinning models based on profitability calculations by three and five per cent proved to be economically better than the thinning models of Tapio when measured by the net incomes and logging costs. Also, just the postponement of the first thinning due to the Tapio's models led to considerably better results than the Tapio's models. Results were parallel to those at the stand and forest holding level. According to the calculations, the thinning model had no impact on the development of the amount of the total removals. However, the thinning models based on the net present value of future revenues by three per cent proved to be best from the point of the development of the forest structure. The share of old and over-aged forests decreased and the financial productivity of the forests improved as compared with timber production programs based on the Tapio's thinning models. Also, the structure of the total removals was characterized by bigger share of saw timber volume.
