Economic Theories, Data, and Graphs: Foundations for Microeconomics

Economic Theories, Data, and Graphs

Positive and Normative Statements

Economists distinguish between two types of statements: positive and normative. Understanding this distinction is fundamental for analyzing economic arguments and policy recommendations.

• Positive statements: These are objective statements about what is, was, or will be. They do not involve value judgments and can be tested against facts.

• Normative statements: These are subjective statements about what ought to be. They depend on value judgments and cannot be evaluated solely by recourse to facts.

• Example: "Increasing the minimum wage will reduce employment among low-skilled workers" is a positive statement. "The government should increase the minimum wage" is a normative statement.

Disagreements Among Economists

Economists often disagree in public discussions, and many of these disagreements stem from the positive/normative distinction.

• Responsible economists clarify which parts of their advice are normative and which are positive.

• Public policy debates often mix factual analysis (positive) with value-based recommendations (normative).

Applying Economic Concepts: Where Economists Work

Economists apply their skills in various sectors of the economy, using analytical methods to evaluate policies and economic risks.

• Governments: Policy analysis, taxation, regulation.

• Private businesses: Market research, forecasting, pricing strategies.

• Crown corporations: Public enterprise management.

• Non-profit organizations: Program evaluation, social impact analysis.

• Post-secondary schools: Teaching, research.

• Example: An economist in government may analyze the effects of a new tax policy on consumer behavior.

Building and Testing Economic Theories

What Are Theories?

An economic theory is an abstraction from reality designed to explain relationships between variables. Theories help economists understand and predict economic phenomena.

• Variables: Quantities that can take on different values.

• Endogenous (dependent) variables: Explained within the theory.

• Exogenous (independent) variables: Determined outside the theory.

• Assumptions: Simplifications to make analysis tractable.

• Predictions: Testable implications derived from the theory.

• Example: In demand theory, price and quantity demanded are variables; price may be exogenous, quantity demanded endogenous.

Testing Theories

Theories are tested by comparing their predictions to real-world evidence. The scientific approach is central to economics.

• If a theory conflicts with facts, it is revised or replaced.

• Empirical testing involves collecting and analyzing data.

• Example: The prediction that "higher prices reduce quantity demanded" can be tested using market data.

Economic Data

Types of Economic Data

Economists use various types of data to analyze economic phenomena.

• Index numbers: Measures of variables relative to a base period (e.g., Consumer Price Index).

• Time-series data: Observations of a variable over time.

• Cross-sectional data: Observations of a variable across different units at a single point in time.

• Scatter diagrams: Graphs showing the relationship between two variables.

• Example: The CPI tracks changes in the average price of a basket of goods over time.

Constructing Index Numbers

Index numbers are calculated to compare values across time or regions.

• Formula:

$\text{Index in given period} = \frac{\text{Absolute value in given period}}{\text{Absolute value in base period}} \times 100$

• Example: If the price of a good is $120 in 2022$ and $100 in 2020$ (base year), the index for 2022 is $\frac{120}{100} \times 100 = 120$.

Graphing Economic Data and Theories

Types of Data Representation

Graphical representation helps economists visualize relationships and trends.

• Cross-sectional graphs: Show data for different units at a single time (e.g., house prices across provinces).

• Time-series graphs: Show data for one unit over time (e.g., unemployment rate from 1978-2021).

• Scatter diagrams: Plot two variables to examine their relationship.

Functions and Relationships

Economic theories often express relationships as functions, showing how one variable depends on another.

• Linear functions: Relationship is a straight line; variables are linearly related.

• Non-linear functions: Relationship is curved; marginal response changes with the value of the variable.

• Example: Consumption as a function of wage income: $C = 800 + 0.8W$

Slope of a Straight Line

The slope measures the rate of change between two variables.

• Formula:

$\text{Slope} = \frac{\Delta Y}{\Delta X}$

• Example: If reducing pollution by 2 units costs $1000, the slope is$\frac{-1000}{2} = -500$.

Non-Linear Functions

In non-linear functions, the slope (marginal response) changes as the value of the independent variable changes.

• Diminishing marginal response: Each additional unit of input yields less output.

• Increasing marginal cost: Each additional unit of output costs more to produce.

Functions with a Minimum or Maximum

Some economic functions have a minimum or maximum point, representing optimal values (e.g., cost minimization, profit maximization).

• Example: Average cost as a function of output may have a minimum at the efficient scale of production.

Summary Table: Types of Economic Statements

Type	Definition	Testable?	Example
Positive	Describes what is, was, or will be	Yes	"A rise in taxes reduces disposable income."
Normative	Describes what ought to be	No	"Taxes should be reduced to increase disposable income."

Final Word

Economic theories and models are essential tools for understanding real-world events. The process of theory development and empirical testing is ongoing, and graphical representation of data is a key method for illustrating economic relationships.