Arrow-Debreu-modell és a Kornai-kritika harminc év után = The Arrow-Debreu Model and Kornai s critique, thirty years after

Több mint harminc év telt el Kornai János Anti-equilibrium című könyvének megjelenése óta. Ez volt az első mű a nemzetközi irodalomban, amely átfogóan bírálta az általános egyensúlyelméletet, mégpedig Debreu értékelméletén és az Arrow-Debreu modellen keresztül. A kritikára legélesebben Frank H. Hahn reagált, amire Kornai - fenntartva korábbi bírálatainak többségét - a közelmúltban megjelent önéletrajzában tért vissza. E cikkben elmélettörténeti előzményekkel együtt rekonstruáljuk a Kornai-Hahn-vita főbb pontjait, és megvizsgáljuk a kritikák és riposztok érvényességét. Látni fogjuk, hogy a legújabb közgazdasági elméletek nem mindenben igazolták Hahn ellenvetéseit. _______________ More than thirty years have passed since János Kornai s book Anti-Equilibrium appeared. This was the first work in international literature to criticize comprehensively the general theory of equilibrium, moreover through the value theory of Debreu and the Arrow-Debreu Model. The sharpest reaction to the criticism came from Frank H. Hahn, and Kornai returned to this in his recent autobiography. This article reconstructs the main points in the Kornai-Hahn debate, including its antecedents in the history of theory, and examines the validity of the criticisms and ripostes. It will be seen that Hahn s objections have not been endorsed in every respect by the latest economic theories.

Rainforests at the beginning of the 21st century

Rainforests are situated at low latitude where forests enjoy steady and strong radiation. Biodiversity in rainforests has been very high, for historical and climatic reasons. The number of species is very high and tends to increase with precipitation and decrease with seasonality. Disturbance, soil fertility and forest stature also influence the species richness and high turnover of species contribute to diversity. Field observation and studies revealed that large scale deforestation could alter the regional and global climate significantly. Deforestation alters the surface albedo which leads to climate change. Regional land use contributes to climate change through surface-energy budget, as well as the carbon cycle. Forest fragmentation, logging, overhunting, fire and the expanding agriculture threaten the biodiversity. Rainforest covered area has significantly shrunk in the last decades. It is hard to protect the forests because of the growing demand for agricultural area and forest-derived products. Most measures proved ineffective to slow down the destruction. Hence, more forest will be lost in the future. Conservationists should take into consideration the secondary forests because biodiversity can be high enough and it is worth protecting them.