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 actually 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: "The unemployment rate is 6%." (positive) vs. "The government should reduce unemployment." (normative)

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 (value-based) and which are positive (fact-based).

• Public policy debates often mix both types of statements, making clear communication essential.

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.

• Employment sectors:

  • Governments

  • Private businesses

  • Crown corporations

  • Non-profit organizations

  • Post-secondary schools

• Economists design methods to analyze and evaluate government policies, examine global economic risks, and study economic growth.

Building and Testing Economic Theories

What Are Theories?

An economic theory is an abstraction from reality that helps explain and predict economic phenomena. Theories are built from variables, assumptions, and predictions.

• Variables: Quantities that can take on different values.

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

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

• Assumptions: Simplifications or conditions under which the theory operates.

• Predictions: Statements about what will happen under certain conditions.

Testing Theories

Theories are tested by comparing their predictions with empirical evidence. The scientific approach is central to economics.

• If a theory conflicts with facts, it is either amended or discarded in favor of a superior theory.

• Empirical testing and refinement are ongoing processes in economic research.

Economic Data

Types of Economic Data

Economists use various types of data to analyze economic phenomena. Understanding these types is crucial for interpreting economic research.

• Index numbers: Measures of variables expressed relative to a base period (assigned value 100). Example: Consumer Price Index (CPI).

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

• Cross-sectional data: Observations of a variable at a single point in time across different units (e.g., provinces, firms).

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

Formula for Index Numbers

The value of an index in a given period is calculated as:

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

Graphing Economic Theories

Functions and Relationships

Economic theories often express relationships between variables as functions. Graphs are used to visualize these relationships.

• Function: If variable Y depends on variable X, Y is a function of X ($Y = f(X)$).

• Functions can be expressed verbally, in tables, mathematically, or graphically.

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

Types of Relationships

• Positive relationship: Two variables move together (increase or decrease simultaneously).

• Negative relationship: Two variables move in opposite directions.

• Linear relationship: Graphed as a straight line; the rate of change (slope) is constant.

• Non-linear relationship: Graphed as a curve; the rate of change (slope) varies.

Slope of a Straight Line

The slope measures the marginal response of one variable to a change in another. For a straight line, the slope is constant.

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

• Example: If reducing pollution by 1 unit costs $1000, and increasing pollution by 2 units costs $2000, the slope is $0.5$.

Non-Linear Functions

In non-linear functions, the slope changes as X changes. This means the marginal response of Y to a change in X depends on the value of X.

• Diminishing marginal response: Each additional unit of X leads to a smaller increase in Y.

• 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 or critical values.

• Example: Average cost as a function of output may have a minimum point, indicating the most efficient scale of production.

Correlation versus Causation

Understanding the difference between correlation and causation is essential for interpreting economic data.

• Positive correlation: X and Y move together in the same direction.

• Negative correlation: X and Y move in opposite directions.

• Correlation does not imply causation; advanced statistical techniques are required to establish causal relationships.

Controlled Experiments in Economics

Economists are interested in causal relationships but often lack the ability to conduct controlled experiments. Recently, randomized controlled trials (RCTs) have been adopted to determine causality among economic variables.

• RCTs help isolate the effect of one variable on another by random assignment.

Summary Table: Types of Economic Data

Type of Data	Description	Example
Index Number	Relative measure to a base period (value 100)	Consumer Price Index (CPI)
Time-Series Data	Observations over time	Unemployment rate from 1978-2021
Cross-Sectional Data	Observations at one time across units	House prices in Canadian provinces in 2021
Scatter Diagram	Graph of two variables for multiple observations	Income vs. consumption for households

Final Word

Economic theories and models are developed to understand real-world events. Theories are continually tested and refined through empirical observation and statistical analysis. Graphs and data visualization are essential tools for illustrating economic relationships and testing predictions.