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Thesis Title Thai Natural Rubber Price Simulation and Stability Analysis

based on Polynomial Fits

Author Mr. Chakkraphong Tomood

Major Program Applied Mathematics

Academic Year 2016

ABSTRACT

Natural rubber is one of the most important agricultural product of Thailand.

Since the movement of the natural rubber price is similar to the stock price, it is
interesting to study its pattern. Most of the work considered prices as continuous

processes which are modeled based on Brownian motion having a continuous sample

paths. However, many small and large changes of the rubber price observed by eyes
brought to the question of jumps. This research aims to simulate the Unsmoked Sheet

Rubber (USS) price of Hat Yai market starting from January 3, 2007 to February 27,
2015 with two models. One is when the price is assumed to be continuous, the other is

when it is assumed to have jumps. A better simulation result is measured by a smaller
value of Average Relative Percentage Error (ARPE), showing that the model with

jump provided an approximately better fit than the continuous model. Moreover, this

research also studies stability analysis of the USS price in a short interval of time in
which the price is fitted with the polynomials up to degree three. The results showed

that the number of equilibrium points and their stability behaviors varied by the

polynomial fitting and the price. However, no matter the equilibrium point is stable or
not a farmer can make an appropriate decision according to the stability behaviors and

the current price.