Pl-5-3 
Where, 
ji(t) equals the ratio of new job opening relative to 
the number of accumulated job aspirants in period t 
and calculated as 
jr(t) = Y Nu(t)/(N(t)-N u (t)) (4) 
Where, 
y: Rate of growth of employment in the urban 
sector (y = A.-p, k is rate of growth of 
industrial output and p is rate of labor 
productivity growth). 
N: Total urban labor force 
N u : Employed labor force in urban sector. (Cole 
and Sanders, 1985) 
This basic concept of Todaro model was further 
elaborated and extended by Harris and Todaro (1970) 
and this model become popular by the name of 
Harris-Todaro (HT) model. 
There are several critiques on this model. According 
to Yap (1977), besides wage and unemployment rate, 
degree of urbanization, spatial distance and flow of 
information have log linear relationship with 
migration. Fields (1975) extended HT model by 
considering the allowances for more generalized job- 
search behavior, an urban traditional sector, 
preferential hiring by educational level and labor 
turnover considerations. 
Similarly, there are several literatures on migration 
where the HT model has been referred argued and 
criticized. Most of the comments are positive and 
several additional factors, which are considered as 
the reason for migration, were pointed out. Still most 
of them agree with the essence of the model. 
3 PRESENT CONCEPT AND PROBLEMS 
The model addresses the wage difference and the 
unemployment and, in general, the critiques are 
mostly related to the economic factors. There is not 
any alternative model along with empirical 
verification to address this problem. Little 
consideration of the rural sector, where most of the 
migration originated, can be seen every where. 
Therefore, it might be reasonable to consider the 
following topics: • 
• Spatial concern of migration should be paid 
attention. 
• Why the migration originated from the rural 
area? Is the high urban wage is sole cause for the 
pull force? What is real push force of the rural 
sector? 
• The empirical study of the cause of rural-urban 
migration and lack of suitable data for such 
study. 
• Rural and urban amenities and the concept of 
RDP, that is Regional Development Potential, 
may have some correlation in migration 
decision. There are two aspects of the RDP that 
are natural and institutional potentiality, which 
again includes a list of parameters. For example 
the soils, water, forest, infrastructure volume, 
population. 
Todaro model is robust model while considering its 
theoretical aspect, but the validation of the model 
with enough empirical data is itself a question. In 
developing countries, the lack of data is another 
problem. Furthermore, Todaro model is formulated 
by considering wage rates, which some times do not 
reflect the real income of the agrarian community. 
This is very important, especially, when the majority 
of the population are engaged in the sustainable 
agriculture, that is the labor force on the farm is 
provided mainly from the family. Besides this, the 
farming practices are also not specialized with any 
particular crop or animal. 
4 CONCEPTUAL FRAMEWORK OF THE 
STUDY 
The socioeconomic (more specifically economic) 
reason and the natural resources condition of the rural 
area are the two different aspect which should paid 
attention while trying to solve the problem of 
migration with policy intervention. There are many 
other factors, like amenities, regional disparity etc.; 
which also influence, directly or indirectly, the 
migration decision. Based on the conceptual 
framework as shown in Fig. 1, for developing 
countries like Thailand, the migration model will be 
formulated. 
The real income (wage) of the agrarian society 
depends directly on the agricultural production which 
intern depends upon the soil productivity. 
Furthermore, soil productivity depends upon the soil 
fertility, which is the function of several parameters. 
The wage philosophy here is not any fixed wage for 
some region from some institute, rather it is the wage 
that comes from the farm where the family member 
had worked. With income theory, the rural income is 
wage plus property (land) income. Thus the rural 
income is the function of agriculture production and 
can be written as: 
Ir = fVr+f(A p S p Sp) (5) 
Where, 
I r : Rural income.