Temi d'esame svolti di Regional Economics - 2° parziale - voto 30

Hoyt's model

Aim

The aim of the model was to predict the physical growth of the city. More precisely, Hoyt was asked by the Chicago housing authority to predict how many houses would have been requested by citizens, because he was an urban planner. So the aim of the model was to forecast the no. of people that could have moved to the city and, as a consequence, how many houses.

Assumptions

• Uniform-abstract space
• The no. of people working in the base sector is exogenously known E_B = E_b. The base sector is the field in which the area specializes.
• People move if there is a job available for them.
• There is a simple direct proportionality between total employment and the people resident in the area P = b.E_T

Logic

The model explains growth in terms of the increase in employment (Total) which, in its turn, depends on the increase in E_B. Being an urban planner, he explains the model using only physical variables.

Hoyt started from the no. of employers working in Chicago and divided them into 2 groups:

E_D = E_B

E_S = a . E_T

E_T = E_B + E_S

E_T = E_B + a . E_T

E_T(1 - a) = E_B → E_T = ¹/_(1-a) E_B

Urban multiplier. It’s ≥ 1.

In growth rate terms:

ΔE_T = ¹/_(1-a) . ΔE_B

Cap 5: Hoyt's model

Aim

a) Aims = The aim of the model was to predict the physical growth of the city. More precisely, Hoyt was asked by the Chicago housing authority to predict how many houses would have been requested by citizens, because he was an urban planner. So the aim of the model was to forecast the no. of people that could have moved to the city and, as a consequence, how many houses.

Assumptions

b) Assumptions

• Uniform-abstract space
• The no. of people working in the base sector is exogenously known. E_D = E_B, the base sector is the field in which the area specializes.
• People move if there is a job available for them.
• There is a simple direct proportionality between total employment and the people resident in the area P = b.E_T

Logic

c) Logic

The model explains growth in terms of the increase in employment (ETOT) which, in its turn, depends on the increase in EB. Being an urban planner, he explains the model using only physical variables.

Hoyt started from the no. of employers working in Chicago and divided them into 2 groups:

E_D = E_B

E_S = a. E_T

E_T = E_B + E_S

E_T = E_B + a.E_T

Base sector E_B = is the sector in which the area specializes and that is able to export the goods produced because there is a surplus

E_T = E_B = exogenous

Service sector E_S = It comprises all the other sectors and it is calculated as a share "a" of E_T -> E_S = a. E_T

0 ≤ a ≤ 100%

E_T - a.E_T = E_B => E_T = ¹⁄_(1-a) E_B Urban multiplier. It is ≥ 1.

In growth rate terms:

ΔE_T = ¹⁄_(1-a) . ΔE_B

* This equation says that if we know the change in Employment in the base sector (ΔE_T), we can calculate the increase in total Employment.

If we assume that each new employee brings with him a number "b" of other people, we can deduct the increase in population.

P = b·E_T → ΔP = b·ΔE_T → ΔP = ^{b · ΔE_T}/_{(1 - A)}

Physical growth of the area.

So from the knowledge of the ΔE_T b, the model determines the physical growth of the area (in terms of population ΔP).

Results

d) Results

The absolute increase in units of employment generates and influences the local growth, in terms of physical growth in population. ΔE in base sector determines an increase in population.

Limits

e) Limits

• The model is unable to explain the ΔE_E because it's exogenously determined.
• It's very simple but it worked for the USA.
• This model describes only a short-term growth path. It can't be used for long-term prediction.
• It takes for granted that the area has available production capacity.
• Constant ratio betw