05

Week 5 · Interactive Visualizations

Production Theory

Prof. Naveen Sunder

Fig 5.1 Total Product & Marginal Product Animator

Drag the worker slider to move simultaneously on both panels. The top panel draws a tangent line on the TP curve (whose slope is MPL); the bottom panel lights up the corresponding MPL point. This makes the "MPL = slope of TP" relationship viscerally clear. Notice that as you increase the number of workers, the marginal product of labor falls -- this is the Law of Diminishing Marginal Product: each additional worker adds less to total output than the previous one (assuming capital is held fixed).

Production function:
Cobb-Douglas: Q = K0.5 · L0.5. Output is always positive and always increasing in L, but at a decreasing rate. This is the most common textbook production function. MPL falls as L rises (diminishing returns), but never reaches zero.
Total Product (TP)
Marginal Product of Labor (MPL)
Workers L: 3.0
Capital K: 4
Fig 5.2 Isoquant & Indifference Curve Explorer

Compare three production technologies side by side: Cobb-Douglas (smooth convex curves), Perfect Substitutes (straight lines), and Leontief / Perfect Complements (right-angle L-shapes). Toggle between Isoquant mode (firm -- axes L and K) and Indifference Curve mode (consumer -- axes X and Y). The math is identical; only the economic interpretation changes. Drag the red dot on the Cobb-Douglas panel to see how MRTS changes along a curve.

Cobb-Douglas
Perfect Substitutes (Linear)
Perfect Complements (Leontief)
Fig 5.3 MRTS Live Calculator

Drag the point along the isoquant Q = K0.5L0.5. As you move right (more L, less K), the annotation updates: "At this point, 1 worker replaces X machines." The tangent line redraws and MRTS = K/L updates in real time.

Isoquant Q = 4 (K0.5L0.5) with Tangent (drag left/right)
Fig 5.4 Diminishing MP vs Decreasing Returns to Scale

The same Cobb-Douglas function Q = KaLb can simultaneously exhibit diminishing MPL AND increasing returns to scale. Left panel: hold K fixed, vary L and watch MPL fall. Right panel: scale both K and L proportionally and watch output more than double.

a (capital exponent): 0.60
b (labor exponent): 0.60
MPL (K fixed = 4)
Scale Both Inputs (L)
Fig 5.5 Returns to Scale Isoquant Spacer

A ray from the origin cuts through three isoquants (Q = 1, 2, 4). Under CRS the intersection points are equally spaced; under IRS they bunch up; under DRS they spread out. Type in exponents a and b and watch the spacing animate live.

a:
b:
Fig 5.6 Input Substitution vs Technological Change

Two fundamentally different actions can change how a firm produces. Pressing "Substitute Inputs" moves the production bundle along the existing isoquant - technology unchanged. Pressing "Improve Technology" shifts the entire isoquant inward - fewer inputs can now produce the same output.

Fig 5.7 Consumer-Production Analogy Side-by-Side

The consumer and the firm face mathematically identical optimisation problems. Left: indifference curve, MRS, budget line. Right: isoquant, MRTS, isocost line. Moving the slider shifts the reference curve on both sides simultaneously.

Utility/Output level: 3.0
Consumer: Indifference Curve + Budget Line
Firm: Isoquant + Isocost Line
Fig 5.8 Cobb-Douglas Production Function Lab

Set A, a, b using sliders. Live outputs: (1) isoquant map with spacing, (2) CRS/IRS/DRS verdict, (3) MPL and MPK evaluated at (K, L), (4) MRTS at that point. The scale-by-lambda slider directly tests the returns-to-scale definition.

Q = 1.0 × K0.50 × L0.50
A: 1.0
a (K exponent): 0.50
b (L exponent): 0.50
K point: 4.0
L point: 4.0
Scale λ: 1.0
Fig 5.9 Bakery / Factory Scenario Simulator

A bakery has a fixed number of machines (K fixed). Hire workers one at a time and watch TP, MPL, and running wage cost update. At some point MPL turns negative and the simulator refuses the hire. Optionally buy a new machine to shift the TP curve upward.

Wage w: $15
Fig 5.10 Isoquant Shape Identifier Quiz

A production function appears. Predict the isoquant shape before it renders, then check if you are right. Covers all three types: smooth convex (Cobb-Douglas), straight line (linear / perfect substitutes), and L-shaped (Leontief / fixed proportions).