Economic Theories, Data, and Graphs: Foundations for Economic Analysis

Economic Theories, Data, and Graphs

Introduction

This chapter introduces the foundational concepts used by economists to analyze and interpret economic phenomena. It covers the distinction between positive and normative statements, the process of building and testing economic theories, the types and uses of economic data, and the graphical representation of economic relationships.

Positive and Normative Statements

Definitions and Distinctions

• Positive statements are objective claims about what is, was, or will be. They can be tested and validated by reference to facts.

• Normative statements are subjective claims 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

• Public disagreements among economists often stem from the positive/normative distinction.

• Responsible economists clarify which parts of their advice are based on facts (positive) and which are based on values (normative).

Applying Economic Concepts: Where Economists Work

Roles and Applications

• Economists are employed in various sectors, including:

  • Governments

  • Private businesses

  • Crown corporations

  • Non-profit organizations

  • Post-secondary schools

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

Building and Testing Economic Theories

What Are Theories?

• A theory is an abstraction from reality, used to explain and predict economic phenomena.

• Theories consist of:

  • Variables: Quantities that can take on different values.

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

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

  • Assumptions: Simplifying statements about the world.

  • Predictions: Testable implications derived from the theory.

Testing Theories

• Theories are tested by comparing their predictions with empirical evidence.

• If a theory conflicts with facts, it is either amended or replaced by a superior theory.

• The scientific approach—systematic observation, hypothesis formation, and testing—is central to economics.

Economic Data

Types of Economic Data

• Index numbers: Measures of variables relative to a base period (base = 100).

• 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., regions, firms).

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

Constructing Index Numbers

• Index numbers are calculated as:

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

• The Consumer Price Index (CPI) is a common example, measuring the average price paid by consumers for a basket of goods and services.

Graphing Economic Data

Types of Graphs

• Cross-sectional graphs: Show data for different units at a single point in time.

• Time-series graphs: Show how a variable changes over time.

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

Example: A cross-sectional graph might show average house prices across provinces in a given year; a time-series graph might show the unemployment rate over several decades.

Graphing Economic Theories

Functions and Relationships

• If variable Y is determined by variable X, Y is a function of X: $Y = f(X)$.

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

• Linear functions: Graphed as straight lines; the relationship between variables is constant.

• Non-linear functions: Graphed as curves; the relationship between variables changes as X changes.

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

Slope of a Straight Line

• The slope measures the change in Y for a one-unit change in X.

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

• Positive slope: variables move together (positively related).

• Negative slope: variables move in opposite directions (negatively related).

Non-Linear Functions

• In non-linear functions, the slope (marginal response) changes as X changes.

• Examples include diminishing marginal returns (decreasing slope) and increasing marginal costs (increasing slope).

Functions with a Minimum or Maximum

• Some functions have a minimum or maximum point, representing the lowest or highest value of Y for a given X.

• These points are important in economic analysis, such as finding the cost-minimizing or profit-maximizing output.

Correlation versus Causation

Understanding Relationships

• Correlation means two variables move together, but does not imply one causes the other.

• Causation means a change in one variable directly causes a change in another.

• Establishing causality often requires advanced statistical techniques or controlled experiments.

Example: Ice cream sales and drowning incidents may be correlated (both rise in summer), but one does not cause the other.

Controlled Experiments in Economics

• Economists often cannot conduct controlled experiments, but recent advances include the use of randomized controlled trials (RCTs) to establish causality.

Summary

• Economic theories are developed to explain and predict real-world events.

• Theories are tested and refined through empirical observation and data analysis.

• Graphs and data visualization are essential tools for illustrating economic relationships.