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Intermediate Microeconomics. Budget Sets. Consumer Theory. First part of class we want to understand “demand”. We want to do so from “first principles”. Consumer Theory - a model to describe how individuals behave. How do individuals choose what to consume?
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Intermediate Microeconomics Budget Sets
Consumer Theory • First part of class we want to understand “demand”. • We want to do so from “first principles”. • Consumer Theory - a model to describe how individuals behave. • How do individuals choose what to consume? • How do these decisions respond to changes in the environment? • How can we use this model to describe market demand for goods? • How should we start?
Budget Set • Consumption Bundle – A list of numbers indicating how much of each good an individual is consuming: {q1, q2, …., qn} • Ex: Suppose there are two goods, peanuts and beer. • {5,12} is a consumption bundle containing 5 oz. of peanuts and 12 oz of beer. • {20,6} is a consumption bundle containing 20 oz of peanuts and 6 oz of beer. • Budget Set – the set of consumption bundles of goods a person can afford. • What does an individual’s Budget Set depend on?
Budget Set • Suppose you are endowed with $10 (i.e. m = 10) and only goods you consume are peanuts and beer. • Peanuts cost $0.10/oz (i.e. pp = 0.10) • Beer costs $0.20/oz (i.e. pb = 0.20) • How can we fully describe your budget set? • Analytically? • Graphically?
Budget Set • Interpreting prices • As we will see, prices will play a big role in our analysis of consumer behavior. • How would we describe the price of an ounce of beer intuitively? • So what would slope of budget set look like if you lived in London, were endowed with 5 pounds, and where: • Peanuts cost 0.5 pence/oz • Beer costs 0.10 pence/oz
Graphing Budget Sets • Slope of budget constraint is rise/run or simply negative of price ratio (-p1/p2). • So how do we interpret this slope? q2 m/p2 1 -p1/p2 q1 m/p1
Graphing Budget Sets • What happens when relative prices change? • (original) m = 10, pp = 0.10 and pb = 0.20 • m = 10, pp = 0.20, and pb = 0.20 • m = 10, pp = 0.10 and pb = 0.10
Graphing Budget Sets • What happens when endowment changes but relative prices don’t? • (original) m = 10, pp = 0.10 and pb = 0.20 • m = 20, pp = 0.10, and pb = 0.20 • m = 4, pp = 0.10 and pb = 0.20
Budget Sets and Taxes • Suppose m = $10, pp = 0.10, and pb = 0.20 • How would budget set change if a 25% sales tax were imposed on beer? • How about if a 25% sales tax were imposed on all goods? • How about if a 25% tax were imposed on each person’s endowment?
Is two-good framework sufficient? • With two goods, we could write a budget set as : p1q1 + p2q2≤ m • Suppose we are interested in analyzing good 1, but there are two other goods that a consumer can also spend money on. • Analyze good 1 compared to a composite good which is just the amount of money spent on all other goods (i.e. goods 2 and 3). • Denoting “dollars” of composite good as qc we can write budget set as: • qc + p1q1≤ m • p2q2 + p3q3≤ qc • If we are only interested in analyzing good 1, we can ignore equation 2, and we are back in two-good framework. • How would we draw this? What is slope?
More Complicated Budget Constraints • Budget constraints seem pretty simple, why do we make them so complicated? • Consider more complicated pricing schemes. • Bulk Pricing • Hamburger is $2/lb for first 3lbs, but only $1/lb for each additional amount past 3lbs.
More Complicated Budget Constraints • Government policy can also often make budget constraints more complicated • Food Stamps • pre-1979 – qualifying “poor” households could “buy” up to $200 worth of food stamps/month at a rate of $1 worth of food stamps for $0.50. • post-1979 - qualifying “poor” households given $100 in food stamps. • How do budget sets differ across two programs for a person earning $300/mo.?
More Complicated Budget Constraints • Public housing • Suppose a person is given a take-it-or-leave-it offer of a free apartment • Further suppose this apartment would rent for $300/month in the marketplace. • If person had $500/mo. in income, what would budget constraint look like? • What if instead of this “in-kind” benefit, person was given $300 in cash. • What would budget constraint look like? • So why don’t we always give cash benefits?
Budget Constraints more broadly • Suppose you worked for Doctors without Borders. • Your funds are enough to have twenty “beds” in your clinic. • Each malaria patient you treat needs one week in your clinic for full treatment. • Each tuberculosis patient you treat needs two weeks in your clinic for full treatment. • What is monthly budget constraint? What is the “cost/price” of treating a tuberculosis patient?