Labor economics Study Guide

📖 Core Concepts Labour Force – All working‑age people who are employed or actively looking for a job. Labour‑Force Participation Rate (LFPR) – Share of the adult population that is in the labour force: $$LFPR = \frac{LF}{Population}$$ Unemployment Rate – Share of the labour force that is not employed: $$u = \frac{U}{LF}$$ Natural vs. Cyclical Unemployment – Natural unemployment = frictional + structural (the “full‑employment” floor). Cyclical (demand‑deficient) unemployment occurs when aggregate demand is too low, pushing unemployment above the natural rate. Labour Supply – Workers choose hours of work $L$ vs. leisure $A$ to maximise lifetime utility, subject to the time constraint $k = L + A$. Labour Demand – Firms hire up to the point where Marginal Revenue Product of Labour (MRP\L) equals the Marginal Cost of Labour (w). $$MRPL = P \times MPL$$ Monopsony – Single (or few) employer(s) dominate the market, driving wages and employment below competitive levels. Information Asymmetry – Employers cannot perfectly observe worker effort (moral hazard) or ability (adverse selection); education can act as a signal. Inequality & Discrimination – Measured with the Gini coefficient; wage gaps may arise from skill differences or discriminatory tastes (Becker) – the Oaxaca decomposition separates the two. --- 📌 Must Remember Unemployment Rate = $U/LF$; LFPR = $LF/Population$. Natural Rate of Unemployment = frictional + structural (excludes cyclical & seasonal). Supply Decision Rule: Work until wage = MRS (leisure, income). Demand Decision Rule: Hire until $w = MRPL$. Substitution Effect (higher w → work more) vs. Income Effect (higher w → afford more leisure). Net supply depends on which dominates. Monopsony Wage is below the competitive equilibrium; employment is also lower. Signalling: Education ↑ → higher perceived ability → higher offered wage, even if productivity unchanged. Oaxaca Decomposition: Wage gap = (explained by skills) + (unexplained = discrimination). --- 🔄 Key Processes Deriving the Labour‑Supply Curve Start with utility maximisation → set w = MRS. Plot labour hours vs. wage; trace substitution vs. income effects. Deriving the Labour‑Demand Curve Compute $MPL$ (additional output from one more worker). Multiply by output price $P$ → $MRPL$. Hire until $w = MRPL$. Finding Competitive Equilibrium Overlay aggregate supply and demand curves. Intersection gives equilibrium wage $w^$ and employment $E^$. Monopsony Hiring Decision Marginal labour cost exceeds the wage because hiring an extra worker pushes up the wage for all workers. Choose $L$ where $MCL = MRPL$ (MCL > w). Oaxaca Decomposition Steps Estimate wage equations for each group (e.g., men vs. women). Decompose the difference into: Explained part = differences in observable characteristics (education, experience). Unexplained part = coefficient differences (interpreted as discrimination). --- 🔍 Key Comparisons Frictional vs. Structural Unemployment Frictional: Short‑run job search & matching; normal even in a healthy economy. Structural: Mismatch of skills/locations; requires retraining or relocation. Competitive Market vs. Monopsony Competitive: Wage = marginal factor cost; supply perfectly elastic; employment maximised. Monopsony: Single buyer; wage < marginal factor cost; lower employment. Income Effect vs. Substitution Effect (wage rise) Income: Higher wage → can afford more leisure → labour ↓. Substitution: Higher wage makes leisure relatively more expensive → labour ↑. Taste‑Based vs. Statistical Discrimination (Becker vs. signalling) Taste‑Based: Employer’s prejudice adds a “psychic cost” → hires fewer minority workers. Statistical: Uses observable proxies (e.g., education) to infer ability; can be efficient but may reinforce gaps. --- ⚠️ Common Misunderstandings “Unemployment rate = % of total population” – It is % of the labour force, not the whole adult population. “Higher minimum wage always raises employment” – In a competitive market it may reduce employment; in a monopsony it can raise both wages and jobs. “All education raises productivity” – In signalling models, education may increase wages without raising actual productivity. “Natural unemployment = zero unemployment” – Natural rate is positive (frictional + structural) and represents the economy’s floor. “Monopsony only exists in tiny towns” – It can arise in any market with few large employers (e.g., tech platforms, franchise chains). --- 🧠 Mental Models / Intuition Budget‑Line Pivot – Imagine a seesaw: a higher wage tilts the line outward; the worker “decides” where to sit (leisure vs. work) where the seesaw balances (MRS = w). Marginal Revenue Product = Value of the Last Unit – Think of each worker as a tiny “factory” that adds a slice of revenue; you keep hiring until that slice equals the cost of hiring. Monopsony as a “Buyer’s Market” – Just like a single supermarket setting prices for farmers, a single employer can push wages down because workers have few alternatives. --- 🚩 Exceptions & Edge Cases Backward‑Bending Supply Curve – At very high wages, the income effect can dominate, causing labour supply to fall. Seasonal Unemployment – Not part of the natural rate; it’s a predictable cyclical pattern (e.g., agriculture). Multiple Equilibria in Search Models – Different matching efficiencies can lead to high‑unemployment or low‑unemployment steady states. Minimum Wage in a Monopsony – May increase both wages and employment up to the competitive level; beyond that, it behaves like a competitive floor. --- 📍 When to Use Which Choose the Labour‑Supply framework when the question asks about worker responses to wage changes, taxes, or welfare benefits. Use the Labour‑Demand (MRP) rule for firm‑side decisions on hiring or for analyzing the impact of capital deepening. Apply Monopsony analysis when the market description mentions a single dominant employer or “few buyers.” Deploy Signalling vs. Human‑Capital models based on whether education is assumed to raise productivity (human capital) or merely convey ability (signalling). Utilise Oaxaca decomposition when asked to separate wage gaps into skill vs. discrimination components. --- 👀 Patterns to Recognize “Wage ↑ → labour ↑ (or ↓)” → Look for wording about “normal good” (leisure) to decide which effect dominates. “Firm faces rising marginal cost of labour” → Indicates monopsony (MCL > w). “Unemployment above natural rate” → Cyclical unemployment → likely a demand‑deficiency shock. “Education raises wages but not productivity” → Signalling scenario. “Wage differential persists after controlling for skills” → Discrimination (unexplained Oaxaca component). --- 🗂️ Exam Traps Confusing Unemployment Rate with LFPR – Answer choices may swap numerator/denominator. Remember: unemployment rate = $U/LF$, LFPR = $LF/Population$. Assuming all wage increases raise labour supply – Ignoring the income effect leads to a wrong “always upward‑sloping” answer. Treating monopsony wage as equal to competitive wage – The monopsony wage is lower; a common distractor lists them as equal. Attributing all education effects to productivity – In signalling questions, the correct answer highlights information rather than skill. Omitting the “unexplained” part in Oaxaca – Some choices give only the explained (skill) component; the full decomposition includes both. ---