One of the most complex concepts for my students to internalize when I taught Econ 101 was that of thinking on the margin. You probably remember the theory of diminishing marginal productivity, diminishing marginal returns, and diminishing marginal utility (satisfaction).   For the math inclined, they are functions with a positive first derivative coupled with a negative second derivative.

Economists like to dress up pretty straightforward ideas with very big words, most likely to obfuscate the fact that economics is just reasonably simple logic.

Traders And Investors Must Also Think On The Margin

It is also essential for traders and investors to think on the margin. They must understand and identify the marginal (last) buyers and sellers in the markets they traffic because those buyers and sellers set and determine the market price. It applies to all asset markets, from stocks to residential real estate.

You have undoubtedly heard the adage “retail always buys the top,” which was a reasonably good contrarian indicator before central banks flooded the markets with liquidity and repressed market interest rates. When I was a trader on Wall Street, the Japanese piling into a market was usually a sign of a top. Not because they were inferior but because they had so much asset purchasing power, i.e, money,  and their conservative culture of decision-making by committee almost guaranteed they were always late to the party.

Diminishing Marginal Returns In The Weight Room

I have discovered the law of diminishing marginal returns in the gym, which has changed my life and significantly improved my health.

In their MOOC (massive online open course) – Hacking Exercise For Health. The surprising new science of fitness –  Martin Gibala and Stuart Phillips of McMaster University teach the concept of diminishing marginal productivity or returns in the gym without using the economic mumbo jumbo.   It cut down my workout time from, say, two hours to just 30 minutes, and here’s how.

I used to be very rigid in my workout, never straying from three sets of 10 repetitions. That third set I hated most would slow me down,  procrastinating to pump it out until the cows came home.

Two or three hours in the gym was too much and led to an inconsistent workout schedule and less than optimal health.

I learned from the McMaster MOOC that 85 percent of the benefit of a three-set exercise comes from the first set!  Doing just one set over a 10-week period improves your strength by 30 percent, while doing three sets increases your muscle by 35 percent, just an extra 5 percent increase for the last two sets.

That is the best and most practical example of diminishing marginal productivity or returns I have seen and experienced. The second and third set, though, still improves overall strength, but most of the bang for your buck is in the first set.

I cut my workouts down to just two sets for each muscle group and get in and out of the gym in thirty minutes. I will trade off the extra 7 percent benefit of the third set for a shorter and more consistent and disciplined workout schedule, any day.

Thirty minutes work for me.

Diminishing Marginal Utility (Satisfaction)  

I used a simple golf analogy to teach the concept of diminishing marginal utility, which my students could relate to.

After a four-hour round of golf in the hot sun, the first beer on the 19^th hole tastes fabulous. The second is fantastic but not as awesome as the first. —a classic case of diminishing marginal utility (satisfaction). The third? Call an Uber. We’re talking craft beer, folks, not Coors Light.

Pretty simple, no?

Watch This Video! 

We highly recommend this video, which taught us how to make our exercise more efficient.  The five-minute investment of your time will change and may save your life.