有限理性、有利商機與景氣循環的波動型態

BOUNDED RATIONALITY PROFIT OPPORTUNITIES AND THE OSCILLATION PATTERN OF BUSINESS CYCLE

本文提出一個嶄新的非線性內生景氣循環模型，以研究技術進步、投資短視與景氣波動之間的關連機制，分析方法係採用Lotka-Volterra微分方程組來闡釋景氣循環的內在機制。此一循環機制緣起於關鍵科技突破後造成商業創新叢生，迸發出龐大的有利商機與生產擴張，但是龐大的有利商機誘使短視近利的廠商加速投資，導致有利商機耗用的速度超過自然湧現的速度。一旦有利商機消耗到達某一臨界值，經濟自然就會反轉衰退。景氣波動就是受到這股內生力量與科技創新的外生力量相互糾纏而呈現此消波長的結果。在本模型中，發現不同的有利商機成長模式將呈現不同的景氣波動特質。若有利商機呈固定成長，經濟將呈固定波幅的景氣波動；若有利商機呈邏吉斯成長(logistic growth)，景氣波動的波幅將呈現隨波遞減的現象。此外，本模型援用科技加速發展的事實合理闡釋循環不對稱現象。

This paper develops a nonlinear dynamic model of business cycles to investigate the possible links between technological breakthroughs, investment myopia and business cycles. The modeling is based upon Lotka-Volterra differential equations to capture an inherent mechanism of business cycles. The mechanism is initiated by technological breakthroughs and clustered innovation that generates enormous profit opportunities for investment and thereby triggers an expansion of output. However, the improved profitability carries the seed of its own destruction by engendering an excessively vigorous expansion of investment. Once profit opportunities decrease to a critical level, the economy cannot sustain itself any more and drop subsequently, causing the onset of recession. This endogenous force intertwining with the exogenous force of technological progress generates cyclical fluctuations in economic activity. In the model, the cyclical pattern of the economy is hinged on the growth pattern of profit opportunities. The oscillation of the economy is constant in amplitude as profit opportunities grow at a constant rate, and dies off gradually as the growth of profit opportunities follows a logistic growth pattern. In addition, this model gives a convincing explanation for the phenomenon of cyclical asymmetry by incorporating the fact of accelerating technological progress.