Inventory investment and GDP characteristics in OECD countries

There are very few research studies on macroeconomic inventory behaviour of various countries. It is clear that macro inventories are the results of a large number of individual microdecisions. However, we believe that it is worth analysing how inventories develop in the individual countries and why we can see different tendencies. This paper is the newest piece in a series of studies on the above subject. We use the OECD database to analyse inventory trends between 1987 and 2004 in nine of the most developed economies of the world. Annual inventory investment data are used and their connections with other components of GDP expenditure (governmental and private consumption, investment in fixed assets and foreign trade balance as well as the annual growth rate of GDP) are examined by multi-variable statistical analysis. Conclusions include the steadily decreasing tendency of inventory fluctuations, the varying periods of higher and lower rates of inventory investments and the differences of main influencing factors by country.

Observing population changes of thrips (Thysanoptera) species damaging forced pepper and their natural enemies

By the strengthening of environmental protection and food safety efforts in Hungary, integrated and especially biological pest control methods should increasingly put forward, for which a solid knowledge on the life course and efficiency of natural enemies applied against certain pests is necessary. Pepper has distinguished significance in domestic vegetable forcing, and the profitability of production is determined primarily by the efficiency of the control of thrips pests. This is why we attached great importance to study what results may be expected by introducing arthropod predators (Amblyseius cucumeris, Orius laevigatus) to control thrips species under domestic conditions on rock wool in a long vegetation period pepper culture. We also liked to find out what kind of role the cultivars play in the change of phytophagous and zoophagous populations. The A. cucumeris predatory mite introduced in late January proved to be effective in controlling thrips pests until mid-April. Despite repeated introductions, the predatory bug O. laevigatus (Heteroptera: Anthocoridae) did not proliferate. Among the three pepper cultivars (Hó, Keceli, Titán) grown at Ráckeve, thrips species proliferated in the highest number on cultivar ‘Hó’, while the population of predatory mites was lowest on the cultivar ‘Titán’, compared to the other two cultivars.

Optimal redistricting under geographical constraints: Why "pack and crack" does not work

We show that optimal partisan redistricting with geographical constraints is a computationally intractable (NP-complete) problem. In particular, even when voter's preferences are deterministic, a solution is generally not obtained by concentrating opponent's supporters in \unwinnable" districts ("packing") and spreading one's own supporters evenly among the other districts in order to produce many slight marginal wins ("cracking").

Why (and When) are Preferences Convex? Threshold Effects and Uncertain Quality

It is often assumed (for analytical convenience, but also in accordance with common intuition) that consumer preferences are convex. In this paper, we consider circumstances under which such preferences are (or are not) optimal. In particular, we investigate a setting in which goods possess some hidden quality with known distribution, and the consumer chooses a bundle of goods that maximizes the probability that he receives some threshold level of this quality. We show that if the threshold is small relative to consumption levels, preferences will tend to be convex; whereas the opposite holds if the threshold is large. Our theory helps explain a broad spectrum of economic behavior (including, in particular, certain common commercial advertising strategies), suggesting that sensitivity to information about thresholds is deeply rooted in human psychology.

Competitors are welcome: why incumbents might embrace entrants?

In this article we show that the price and the profit of an incumbent firm may increase after a new firm enters its market. Our analysis suggests that a well-established firm after competition emerges on its market might benefit from excluding some consumers from the low-end segment and concentrate only on its loyal consumers.