AD-AS Model: The Complete Guide to Aggregate Demand & Supply

追加: 2026-06-02

[00:00:00]We're breaking down how a closed economy fights  short-term unemployment using two very different rescue strategies and why the strategy you  pick completely changes the outcome for private businesses. Now, you're probably wondering if the  economy is totally stalled out, does it actually matter who steps in to fix it, the government or  the central bank? Well, we need to look at our first option, which is government action. First,  we have fiscal expansion. When the government ramps up spending or cuts taxes, aggregate demand  shifts, right? Output grows and prices rise.

[00:00:32]But those higher prices shrink real money  balances, which forces interest rates to spike.

[00:00:38]It's kind of like the government stepping  on the gas pedal. Sure, the engine revs up, but that inflation acts like a break on private  businesses trying to get a loan because borrowing gets so expensive, private investment actually  decreases. So, if government spending chokes out private investment, what's our alternative?  Second, let's look at monetary expansion.

[00:00:57]If the central bank lowers the reserve ratio  or buys bonds, they increase the money supply.

[00:01:02]Why does this work better for businesses? While  flooding the system with liquidity pushes interest rates down, making cash super cheap to borrow.  Aggregate demand still shifts, right? Output grows and prices rise, but crucially, investments  absolutely increase. Finally, let's look at the bottom line. Both of these expansions successfully  raise output to fight short-run unemployment. But they have totally opposite effects on investment.  Fiscal expansion shrinks it, while monetary expansion grows it. To cure an unemployment slump,  both government spending and money printing will get the economy moving again. But only the central  bank's method leaves private businesses with the cheap money they need to actually grow. This  is the brief on the ADS macroeconomic model.

[00:01:41]It's the ultimate cheat sheet for how an  economy balances out by tracking two variables, overall price levels and total economic output  or GDP. Ever wonder why inflation and economic growth always seems so tangled up together?  First, let's look at aggregate demand or AD.

[00:01:58]It's the sum of consumer, business, and government  spending. It triggers a wild chain reaction.

[00:02:04]When prices go up, real money supply  shrinks, making interest rates rise.

[00:02:08]That makes borrowing expensive, dropping overall  output. It's kind of like a financial seessaw.

[00:02:13]As prices weigh down one side, business investment  and total output get pushed down on the other.

[00:02:19]Second, we have aggregate supply or as.  It acts totally differently over time.

[00:02:24]In the short run, wages are sticky, so higher  prices tempt producers to manufacture more.

[00:02:29]Wait, if prices go up, can we just trick the  economy into producing more forever? Nope.

[00:02:35]The long run supply curve is completely vertical.  Long-term output relies on real world limits like capital, labor, and technology. Price changes  do nothing to it. It's a hard reality check.

[00:02:46]Finally, know the difference between a movement  and a shift. Changing prices just causes a movement along existing curves. But changing  real factors like the government spending more or a massive tech breakthrough actually shifts the  entire curve. Shifting these curves is exactly how central banks steer us out of recessions.  Ultimately, the ADS model proves the link between prices and economic output isn't random  chaos. It's a highly predictable chain reaction driven by short-term interest rates and the  long-term hard limits of labor and technology.

[00:03:16]Today, we're focusing strictly on the money  market. And I mean absolutely nothing else.

[00:03:20]Setting the stage to understand exactly how  price levels dictate the reality of our money and our borrowing costs. First, let's talk about  the initial trigger where an increase in P, you know, the overall price level directly  leads to a decrease in the real money supply.

[00:03:37]Think about it like this. If the price of your  daily iced coffee suddenly doubles, while that $10 bill in your wallet hasn't physically changed  at all, but its real value and actual purchasing power in the market has essentially shrunk.  Second, we have to look at the domino effect because this drop in the real money supply leads  to a direct increase in the interest rate within the economy. So, if there is effectively  less real money available to go around, what happens when people still need to borrow  it? Naturally, the cost to borrow that money, the interest rate has to go up. Ultimately, when  general prices rise, the real value of the money supply shrinks, which inevitably makes money more  expensive to borrow and drives up interest rates.

[00:04:15]Today, we're diving into a super specific no fluff  directive that demands an explanation of a complex macroeconomic concept, but with some extremely  rigid boundaries. First, the source isolates just one single economic concept, the aggregate supply  curve. You know, it's honestly so refreshing to just strip away all the usual economic noise and  focus purely on the supply side for a change.

[00:04:38]So once we've isolated this curve, we have  to look at the two specific ways the source actually asks us to view it. Second, the text  specifically demands a contrast between SRA or shortrun aggregate supply and LRA, the long run  aggregate supply. To put that into perspective, think of the economy kind of like a runner.  SRA is like a sprinter's immediate short-term burst of speed, right? While LRA, well, that's  their ultimate sustainable marathon pace. Now, moving from those core economic concepts, we  really have to look at the strict parameters the source places on exactly how they should be  discussed. Finally, the real defining feature of this text is its strict negative constraint,  literally instructing us to explain it without expanding beyond that. Now, you might be wondering  why put such a hard fence around a topic. Well, because in really complex subjects, deliberately  blocking out extra information is absolutely the best way to ensure total comprehension of those  core facts. Ultimately, this source is a laser focused demand for a strict zero fluff comparison  between shortrun and long run aggregate supply.

[00:05:39]Today, we're using the aggregate demand aggregate  supply model or ADAS for short as a fun little cheat code to figure out exactly why everyday  stuff keeps getting so expensive. totally saving you from slogging through a dense textbook. First,  when aggregate demand outpaces full employment, prices absolutely skyrocket. You know, you can  think of full employment as the economy's absolute max capacity where factories are completely  maxed out and everyone who can work is literally working. So, imagine a highly anticipated, totally  sold out concert. When buyer demand wildly exceeds the venue's physical capacity, printing more  tickets doesn't magically create more seats, right? It just kicks off a massive bidding war.  Second, this crazy bidding war happens even when prices are considered rigid. Rigid prices are  usually locked into long-term contracts or they're just super slow to change, kind of like printed  restaurant menus. But man, it really makes you wonder if these prices are fundamentally built  to stay put, just how incredibly overwhelming does that excess demand have to be to shatter  those contracts and force prices up anyway?

[00:06:47]Finally, we're left with a real economic  cliffhanger. We know overwhelming demand clearly creates inflation. But here's the catch. We've  only solved the demand side of the whole puzzle.

[00:06:57]If demand isn't the sole culprit, what else  is secretly driving up your grocery bill?

[00:07:01]Ultimately, the ADAS model proves that whenever  demand outpaces an economy's maximum capacity, prices inevitably rise. But it leaves us eagerly  hunting for the other hidden drivers of inflation.

[00:07:13]You know, the ADAS, that's aggregate  demand and aggregate supply model is a massive economic concept. But today,  we're cutting out all that extra noise to focus strictly on the demand side, giving you  a clear look at what truly fuels an economy.

[00:07:29]First, we isolate the aggregate demand or AD  curve. Think of the entire economy as just a giant marketplace. Well, in this scenario, the  AD curve is essentially the master shopping list.

[00:07:42]So, why focus just on this curve? Because you  simply cannot understand the broader market without first grasping the total demand. Second,  let's look at the composition of that demand.

[00:07:53]It's not just a single solid block. It's actively  composed of distinct smaller components like everyday consumer spending, business  investments, and government purchases.

[00:08:03]So why does it matter that it's broken down  into smaller parts? Because you literally can't comprehend the total demand without looking at the  specific ingredients that build the whole shebang.

[00:08:13]Finally, we really have to emphasize the  drivers of each component. Just identifying the pieces isn't enough. If we don't zero in on the  underlying forces moving each individual piece, like how a sudden drop in interest rates  motivates a business to build a new factory, we have absolutely no way to predict how  the overall AD curve is going to shift.

[00:08:33]Ultimately, understanding the demand side means  breaking the aggregate demand curve down into its core components and figuring out the unique  forces driving every single one of them. Once you know exactly what motivates those individual  pieces, you hold the absolute key to understanding how the entire economic engine shifts gears. We're  looking at the mechanics of an economic recession, specifically when prices are rigid or sticky. So,  imagine a giant retail store where customer foot traffic suddenly plummets, but the manager  absolutely refuses to lower the price tags, creating a standoff that directly impacts jobs.  So, how does this actually play out? Well, first, aggregate demand shrinks. Think of this as total  spending in the economy just dropping off a cliff, which causes the AD curve to shift to the left.  Second, the economy actually finds a new balance or equilibrium. But honestly, it's a massive  downgrade. You know, it's essentially stabilizing at a completely broken level, just settling for an  underperformance that sits way below its healthy full employment capacity. Finally, because  production has dropped so far below that full capacity, unemployment naturally grows. But that  leaves us with a pretty huge lingering question.

[00:09:47]What actually drives this initial drop in  demand for output in the very first place?

[00:09:51]Ultimately, when total demand drops and prices  stay rigidly stuck, the economy's output shrinks and unemployment rises, leaving us to hunt for the  exact trigger behind that initial spending freeze.

[00:10:03]Let's say the economy is in a recession with high  unemployment. How does the government fix it?

[00:10:09]By using fiscal expansion. Let's see this in the  ADAS model. Here's the ADAS model. The economy is currently producing below its potential output.  That gap between actual output and potential output is called the recessionary gap. It means  high unemployment and underused resources.

[00:10:29]The government steps in by spending more  or cutting taxes. This injects money into the economy, boosting total demand. The aggregate  demand curve shifts to the right from AD to AD2.

[00:10:42]As a result, businesses hire more  workers to meet the new demand.

[00:10:46]Real GDP increases from Y1 toward  potential output Y2 and unemployment falls.

[00:10:53]But because demand is higher, the price level  also rises slightly, causing some inflation.

[00:10:59]So what's the final result? Real GDP goes up,  unemployment falls, and the price level rises slightly. The recessionary gap is closed, and  the economy returns to its potential output.

[00:11:11]Fiscal expansion works with just a  small trade-off of higher prices.