Biomedical subjects

Kaushik Matia

Publications and source records attributed to Kaushik Matia.

3 recordsLinked to original sources

PubMed2006

Preferential attachment and growth dynamics in complex systems.

Complex systems can be characterized by classes of equivalency of their elements defined according to system specific rules. We propose a generalized preferential attachment model to describe the class size distribution. The model postulates preferential growth of the existing classes and the steady influx of new classes. According to the model, the distribution changes from a pure exponential form for zero influx of new classes to a power law with an exponential cut-off form when the influx of new classes is substantial. Predictions of the model are tested through the analysis of a unique industrial database, which covers both elementary units (products) and classes (markets, firms) in a given industry (pharmaceuticals), covering the entire size distribution. The model's predictions are in good agreement with the data. The paper sheds light on the emergence of the exponent tau approximately 2 observed as a universal feature of many biological, social and economic problems.

Journal Article↗

PubMed2005

The growth of business firms: theoretical framework and empirical evidence.

We introduce a model of proportional growth to explain the distribution P(g)(g) of business-firm growth rates. The model predicts that P(g)(g) is exponential in the central part and depicts an asymptotic power-law behavior in the tails with an exponent zeta = 3. Because of data limitations, previous studies in this field have been focusing exclusively on the Laplace shape of the body of the distribution. In this article, we test the model at different levels of aggregation in the economy, from products to firms to countries, and we find that the predictions of the model agree with empirical growth distributions and size-variance relationships.

Commerce↗

PubMed2002

Different scaling behaviors of commodity spot and future prices.

Classic studies of spot price fluctuations for commodities like cotton and wheat have been interpreted using a power-law probability distribution with exponent alpha inside the Lévy-stable regime (0<alpha<2). In contrast price fluctuations for stocks have been interpreted using a power-law probability distribution with alpha outside the Lévy-stable regime suggesting that stock prices are in a different universality class than spot prices for commodities. To test this possibility we analyze daily returns of spot prices for 29 commodities and daily returns of future prices for 13 commodities over a period exceeding 10 years and find that the distributions of returns for futures decay as power laws with exponents alpha approximately 3.2, significantly larger than alpha=2 and hence outside the Lévy-stable domain, while for spot prices we find alpha approximately 2.3 which appears to be marginally outside the Lévy-stable domain.

Journal Article↗