- [Instructor] In the previous
video, we began our study
of ABC Watch Factory and
we tried to understand
the economics of the
business based on some data
that we had already collected on our costs
and how much output we could produce
based on how many labor units we had.
And then from that, we calculated things,
like the marginal product of labor,
the marginal cost, the
average variable cost,
the average fixed cost,
and the average total cost.
What we're going to do in this video
is take this information,
especially total output
and all of these things
that we just calculated,
so that we can better appreciate
how these various calculations
and the curves that we can
get from the calculations
are interrelated, so let me scroll over
a little bit so we have some space
and then let me set up a
little coordinate plane here.
And so what we have on our vertical axis,
this is our cost, and then down here,
in our horizontal axis this is our output.
So, first let's just hand graph it,
and I encourage you to go
through the exercise yourself.
It's one thing to watch me do it,
but when you actually graph something
you digest the numbers that much better.
And so, let's start with marginal cost.
And I'm going to do it
in this blue-green color.
So let's see, when our total output is 25,
our marginal cost is 267.
So, when our out put is 25,
267 would be right about there.
And we're just trying to get,
be able to visualize what's going on.
And then, when our total output is 45,
our marginal cost is $150.
So 45 is here and then 150
is right about there.
And then when our total output is 58,
our marginal cost is 231.
So 58 is right about there,
and then it's gonna be 231,
so it's about, right about there.
And then, when our total output is 65,
our marginal cost is 429,
so the 65 is right over there
and then 429 will get us right about,
right about there, so you see
our marginal cost is going up a lot now,
it might be a little bit lower than that,
so it's gonna be right over there.
And then last but not least,
when our total output is 70,
our marginal cost is $600.
So at 70 we get to 600
and I'm eyeballing it,
that's not exact graph paper,
but this gives you a sense
of what the marginal
cost curve looks like.
And here we've kinda graphed it based on
where we are in terms of output.
So, that's our marginal,
marginal cost curve.
So I'll just label that marginal cost.
And now let's see how
that relates to the curves
for average variable cost
and average total cost.
So average variable cost
I'll do in this orange color.
So, at an output of 25,
our average variable cost is $240.
So 25, we are going to be
at $240,
which is right about, right about there.
And then when we are at 45 units,
our average variable cost is 200.
So at 45, units our average variable cost
is right over there.
And then at, we did that one.
And then at 58 units, it's $207.
58 units, it is 207,
so it's going to be right about there.
And then at, we did this one.
And at 65 units, it's 231.
65 is, and then we get to 231
which is right maybe about there.
And then, this we did this one,
and then at 70 units, we're at 257.
So 70 units, 257 looks
something like this.
Now, before I actually
draw into this scurve,
connect the dots, so let's just think
about how the average variable cost
relates to the marginal cost.
When the marginal cost is less than
the average variable cost,
well that means that as
we produce more and more,
our average variable cost should go down,
and we see that happening
in this early stage.
I won't go into all the details
on what's happening
exactly right over there,
but that early stage, as we see that
while our marginal cost is less
than our average variable cost,
our average variable
cost is trending down.
And that makes sense.
Every incremental unit
is a little big cheaper
to produce, so it brings down the average.
But as soon as the marginal curve
crosses the average variable cost
and the marginal cost,
every incremental unit
is now more than the average,
well that should bring up the average.
And so then the average variable cost
should start sloping up.
So, it's good to realize,
one is a rule of thumb
but even more important to realize why,
that where the marginal cost curve
and the average variable
cost curve intersect,
that that's going to be the point
at which the average variable cost
goes from trending down to trending up.
If you viewed as this very wide U shape,
that would be the bottom of the U.
And we can do the same thing thing
with average total costs.
Now, they're going to
cross a little bit later
because the average total costs are higher
because they're factoring
in the fixed costs as well,
but you can imagine that
while your marginal costs
are lower than your average total costs,
every incremental unit
is going to bring down
the average total cost, but as soon as
the marginal cost crosses
the average total cost,
it's gonna start bringing up the average.
And we can see that by trying to graph
average total cost, and I'll
do that in this yellow color.
So, at 25 units, we're at 440.
25 units, we're at 440 that makes sense
'cause we have all that fixed cost
that we're spreading along
amongst not that many units.
And then at 45 units, we're at 311.
45 and we get to 311, might
be right around there.
Then at 58 units, we're at 293.
58 units, we are at 293,
which is right about there.
And then at 65 units, we're at 308.
65 units, we are at 308.
And then at 70 units, we're at 329.
70 units, we are at 329,
so it maybe something like this.
And so this is our average total cost.
And just as you can imagine,
while your marginal costs,
every incremental unit, the cost of that,
is less than your average total cost,
it'll bring down, when you
do that incremental output,
it will bring down your
average total costs
until the point that they cross
and then, now, after you,
after these two curves cross,
now every incremental unit is bringing up
the average cost, 'cause it's
costing more than the average.
And so, once again, where
these two curves intersect,
if you view the average total cost curve
where there's this big wide U,
it would represent the bottom of the U.
Now, the last thing that we didn't graph,
and this is maybe the most intuitive,
is the average fixed cost.
And this is just going to asymptote down.
At 25 units, we're at 200.
25 units, we are at 200.
At 45 units, we are at 111.
45, 111, it's maybe right over there.
At 58 units we're at 86.
58 units, 86.
At 65 units, we're at 77.
65 units, 77.
And then at 70 units, we're at 71.
And so you can see that that
just gets lower and lower and lower
over, as you produce more and more output
because you're able to
spread those fixed costs
amongst more and more output,
so that makes sense that
the average fixed costs
just trends downward like
this the entire time.
But the big take-aways here is
not just to understand the rule of thumb
that where the marginal cost curve
intersects the average variable cost
or the average total cost,
that that's the, you could
view it as the minimum point
of the average total cost
or the average variable cost curves,
but to understand why that is happening.
