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Rajesh.K.Chundambatta & Sangeetha.U
GHSS Kodumunda
Palakkad
Plus Two - Economics Chapter 3
Theory of the Firm ..
Production & Cost
• An economic unit that produces goods and
services is called the Producer / Firm
All resources used for production of goods are
called inputs. Land, Labour, Capital, Organisation = Factor inputs
Goods & Services produced using inputs are called
Output
Production refers to transformation of inputs into output.
• Production is the process of combining inputs to make outputs
• The firm buys inputs from households /other firms and sells its output to consumers
PRODUCTION FUNCTION
The relationship between inputs and output
is called production function.
Q = f (X1, X2)
Isoquant
• Isoquant represents all the possible
combinations of two inputs that
produce the same level of output.
The important factor that affect production is time period
Short Run and Long Run
• It is useful to categorize firms’ decisions into
– Short-run decisions
– Long-run decisions
• To guide the firm over the next several years – Manager must use the long-run lens
• To determine what the firm should do next week – Short run lens is best
Short Run
• Short run is the period in which the firm cannot change all inputs
The inputs in short run are classified into two
• Fixed inputs/ Fixed factors – In short run all the factors cannot be varied.
Such factors are called fixed factors.
eg: factory building, new machinery etc.
• Variable input/ Variable factors – Those factors which can be varied in the short run are
called variable factors.
eg: quantity of raw materials,quantity of labour etc
Long Run
• Long run is the period in which the firm can change all inputs
• In the long run all inputs are variable
Short run Production Function
The production function in which application
of one factor is varied, while all other factors
are kept constant is called short run
production function.
It is also known as law of variable proportion
or law of returns to a factor
Long Run Production Function
• In the long run, all factors of production
can be varied.
• A firm in order to produce different levels
of output in the long run may vary all
inputs.
• So, in the long run, there is no fixed input.
It is also known as law of returns to scale/
fixed proportion production function
Total Product (TP)
It is the relationship between a variable input and output, when all other inputs are held constant.
It is the total output at a particular level of employment of a variable input.
Total product is also sometimes called Total Return or Total Physical Product. (TPP)
Average Product (AP)
Average product is defined as the output per
unit of variable input
AP1 = TP
X1
Marginal Product (MP)
MP is defined as the change in output
per unit of change in input, when all other
inputs are held constant.
Marginal product are additions to the total
product.
MP = change in TP
change in variable input
The Law of Diminishing Marginal Product
&
The Law of Variable Proportions
• It is a short run production function.
According to this law if we keep increasing the
employment of an input, with other inputs fixed
eventually a point will be reached after which
the resulting addition of output (i.e. MP) will
start falling.
The Law of variable proportion also
explains that the marginal product of a factor
input initially rises with its employment level.
But after reaching a certain level of
employment, it starts falling.
• According to this theory, as we increase
the variable factor, the TP, AP and MP
passes through three distinct stages.
Stage 1 : Increasing Returns
• In the first stage TP increases at an
increasing rate.
• Then MP also increases and reaches
maximum, AP rising.
Stage 2 : Diminishing Returns
• In this stage MP and AP decline.
But TP continue to rise at a diminishing
rate.
Stage second ends with MP touching zero.
Stage 3 : Negative Returns
• Third stage begins with MP turning
negative.
• TP starts declining
When TP is maximum MP is zero.
When TP declines, MP turns negative.
The Law of Diminishing Marginal Product &
The Law of Variable Proportions
Returns to Scale
( Long Run Production Function )
• In the long run, there is no fixed input.
All factors are variable.
It is known as fixed proportion production
function because input ratios remain the
same.
Increasing returns to scale
• Increasing returns to scale (IRS)
holds when a proportional
increase in all inputs results in an
increase in output by more than
the proportion.
Constant returns to scale
• Constant returns to scale (CRS) is a
property of production function that
holds when a proportional increase in
all inputs results in an increase in
output by the same proportion.
Decreasing returns to scale
• Decreasing returns to scale (DRS)
holds when a proportional increase
in all inputs results in an increase in
output by less than the proportion.
Cobb-Douglas Production Function
• Consider a production function
q = x1α x2
β
where q is quantity of output, α and β are constants.
β = 1- α
The firm produces q amount of output using x1 amount of
factor.1 and x2 amount of factor.2.
• Cobb-Douglas production function is a
linearly homogenous production
function.
That means, if factors are increased ‘t’ times,
output will also increase ‘t’ times where (t > 1).
If α + β = 1, production function is CRS
If α + β > 1, production function is IRS
If α + β < 1, production function is DRS
Costs...
Costs
• In order to produce output, the firm needs to employ inputs.
• Costs refer to the Expenses incurred in
production.
• The firm’s goal is to earn the highest possible profit. To do
this, it must follow the least cost rule
• Wages, rent, interest, transportation etc are examples of
costs
Short Run Costs
• In short run, costs can be classified as TFC and TVC
• Fixed costs
– Costs on fixed factors are called fixed costs.
• Variable costs
– Costs on variable factors are called variable
factors.
Types of Total Costs
– Total Fixed Costs • Cost incurred for the purchase of fixed inputs.
• This Cost do not change with change in output
• eg: rent for land & building, salary etc
– Total Variable Costs • Cost incurred on variable inputs
• This Cost change as output changes
• eg: cost for raw materials, transportation etc
– Total Cost • Cost of all inputs—► fixed and variable
• TC = TFC + TVC
Shape of TFC, TVC and TC
TC
0
Cost
q Output
TFC
TFC
TVC
Short Run Average Costs
• Average fixed cost (AFC)
– Fixed cost per unit of output produced
• Average variable cost (AVC) – Variable cost per unit of output.
• Short run Average Cost
Total Cost per unit of output is called SAC
Q
TFCAFC
Q
TVCAVC
AVCAFC SAC
Q
TCSAC QSACTCie *,
AFC
Product
Cost
Average Fixed Cost Curve (AFC)
Average Variable Cost Curve (AVC)
Cost
AVC
Output
Shape of SAC curve
Output
SAC
Cost
Short run Marginal Cost (SMC)
- Addition to the Total Cost
- Change in TC due to the production of
one extra unit of output
- Tells us how much cost rises per unit
increase in output
ΔQ
ΔTCMC
Relation between SAC and AVC
SMC
AVC
SAC
Output
costs
20
15
10
5
10 30 40 50 60 0 20 70
Long Run Costs
• In the long run, all inputs and all costs are
variable. There are no fixed inputs or fixed
costs.
and Q
TCLRAC
ΔQ
ΔTCLRMC
Shapes of Long run Cost Curves
LRMC
LRAC
DRS IRS q
thank you...