Remembering Jay Forrester

I’m sad to report that Jay Forrester, pioneer in servo control, digital computing, System Dynamics, global modeling, and education has passed away at the age of 98.


I’ve only begun to think about the ways Jay influenced my life, but digging through the archives here I ran across a nice short video clip on Jay’s hope for the future. Jay sounds as prescient as ever, given recent events:

“The coming century, I think, will be dominated by major social, political turmoil. And it will result primarily because people are doing what they think they should do, but do not realize that what they’re doing are causing these problems. So, I think the hope for this coming century is to develop a sufficiently large percentage of the population that have true insight into the nature of the complex systems within which they live.”

I delve into the roots of this thought in Election Reflection (2010).

Here’s a sampling of other Forrester ideas from these pages:

The Law of Attraction

Forrester on the Financial Crisis

Self-generated seasonal cycles

Deeper Lessons



Market Growth

Urban Dynamics

Industrial Dynamics

World Dynamics




Population Growth Up

According to Worldwatch, there’s been an upward revision in UN population projections. As things now stand, the end-of-century tally settles out just short of 11 billion (medium forecast of 10.9 billion, with a range of 6.8 to 16.6).

The change is due to higher than expected fertility:

Compared to the UN’s previous assessment of world p opulation trends, the new projected total population is higher, particularly after 2075. Part of the reason is that current fertility levels have been adjusted upward in a number of countries as new information has become available. In 15 high-fertil ity countries of sub-Saharan Africa, the estimated average number of children pe r woman has been adjusted upwards by more than 5 per cent.

The projections are essentially open loop with respect to major environmental or other driving forces, so the scenario range doesn’t reflect full uncertainty. Interestingly, the UN varies fertility but not mortality in projections. Small differences in fertility make big differences in population:

The “high-variant” projection, for example, which assumes an extra half of a child per woman (on average) than the medium variant, implies a world population of 10.9 billion in 2050. The “low-variant” projection, where women, on average, have half a child less than under the medium variant, would produce a population of 8.3 billion in 2050. Thus, a constant difference of only half a child above or below the medium variant would result in a global population of around 1.3 billion more or less in 2050 compared to the medium-variant forecast.

There’s a nice backgrounder on population projections, by Brian O’Neil et al., in Demographic Research. See Fig. 6 for a comparison of projections.

Braveheart & Rogaine

The Reinhart & Rogoff debt/growth paper continues to make a stir for it’s basic Excel errors. Colbert has the latest & funniest take on it.

Two things about this surprise me.

Confronted with obvious and irrefutable errors, the authors double down and admit nothing. They also downplay the significance of the results, ‘… we are very careful in all our papers to speak of “association” and not “causality” …’

But of course the (amplified) message, Debt/GDP>90%=doom, was taken causally in the policy world; see the multiple clips in the intro to the Colbert video. Politicians are nuts to accord one paper in a sea of macroeconomic thought so much weight, but I guess this was the one they liked.

Politicians designing control systems, badly

We already have to fly in planes designed by lawyers (metaphorically speaking). Now House Republicans want to remove the windows and instruments from the cockpit. This is stupid. Really stupid. I’ve used ACS data on numerous public and private sector consulting engagements. I’m perfectly willing to pay for the data, but I seriously doubt that the private sector will supply a substitute. Anyway, some basic free data is needed so that all citizens can participate intelligently in democracy. Lacking that, we’ll have to fly blind. Say, what’s a mountain goat doing up here in a cloud bank?

A Titanic feedback reversal

Ever get in a hotel shower and turn the faucet the wrong way, getting scalded or frozen as a result? It doesn’t help when the faucet is unmarked or backwards. If a new account is correct, that’s what happened to the Titanic.

(Reuters) – The Titanic hit an iceberg in 1912 because of a basic steering error, and only sank as fast as it did because an official persuaded the captain to continue sailing, an author said in an interview published on Wednesday.

“They could easily have avoided the iceberg if it wasn’t for the blunder,” Patten told the Daily Telegraph.

“Instead of steering Titanic safely round to the left of the iceberg, once it had been spotted dead ahead, the steersman, Robert Hitchins, had panicked and turned it the wrong way.”

Patten, who made the revelations to coincide with the publication of her new novel “Good as Gold” into which her account of events are woven, said that the conversion from sail ships to steam meant there were two different steering systems.

Crucially, one system meant turning the wheel one way and the other in completely the opposite direction.

Once the mistake had been made, Patten added, “they only had four minutes to change course and by the time (first officer William) Murdoch spotted Hitchins’ mistake and then tried to rectify it, it was too late.”

It sounds like the steering layout violates most of Norman’s design principles (summarized here):

  1. Use both knowledge in the world and knowledge in the head.
  2. Simplify the structure of tasks.
  3. Make things visible: bridge the Gulfs of Execution and Evaluation.
  4. Get the mappings right.
  5. Exploit the power of constraints, both natural and artificial.
  6. Design for error.
  7. When all else fails, standardize.

Notice that these are really all about providing appropriate feedback, mental models, and robustness.

(This is a repost from Sep. 22, 2010, for the 100 year anniversary).

Shocking stats from the WSJ

The WSJ has an article on the Chinese electric power sector that’s anecdotally interesting. It notes that increasing electricity prices would spur investment, creating a win-win for energy intensity and system reliability. Maybe so, but the supporting graph is an interesting example of statistics that are uninformative because they fail to account for bathtub dynamics. Here it is:

It seems plausible to compare investment and consumption, until you look at the system structure:

This indicates four problems with drawing conclusions from the plot:

  • Investment is not necessarily the same thing as installation of capacity, unless you assume constant price.
  • Consumption is essentially a direct function of stocks of consuming equipment and generating capacity, while investment is a flow. While there’s reason to expect growth rates of stocks and flows to match along a steady state growth path, this only applies in the very long term; in the short run, noise and disequilibrium will destroy any correspondence.
  • The thing we do care about is the match between generating capacity and consuming equipment, but that depends on outflows (retirements of capacity) as well as inflows, so again the stock-flow comparison tells us nothing.
  • There’s an additional level of indirection because we don’t see investment and consumption directly; the graph shows year-on-year changes. But that means that we’re seeing the slopes of investment and consumption, which tell us nothing about their absolute levels. So, it’s possible that investment growth is falling because it was much too high, and that consumption is growing because there’s excess generating capacity.

The best you can say about this graph is that it doesn’t contradict the article; otherwise it’s almost completely uninformative about the true state of the Chinese power system. It would be far better to have a direct comparison of generating and consuming capacity, or perhaps the growth rate of consumption (which is the net flow of consuming equipment) vs. investment in absolute terms.

The envelope please…

The 2011 Ig Nobel in Mathematics is for modeling … it goes to predictors of the end of the world:

Dorothy Martin of the USA (who predicted the world would end in 1954), Pat Robertson of the USA (who predicted the world would end in 1982), Elizabeth Clare Prophet of the USA (who predicted the world would end in 1990), Lee Jang Rim of KOREA (who predicted the world would end in 1992), Credonia Mwerinde of UGANDA (who predicted the world would end in 1999), and Harold Camping of the USA (who predicted the world would end on September 6, 1994 and later predicted that the world will end on October 21, 2011), for teaching the world to be careful when making mathematical assumptions and calculations.

Notice that the authors of Limits to Growth aren’t here, not because they were snubbed, but because Limits didn’t actually predict the end of the world. Update: perhaps the Onion should be added to the list though.

The Medicine prize goes to a pair of behavior & decision making studies:

Mirjam Tuk (of THE NETHERLANDS and the UK), Debra Trampe (of THE NETHERLANDS) and Luk Warlop (of BELGIUM). and jointly to Matthew Lewis, Peter Snyder and Robert Feldman (of the USA), Robert Pietrzak, David Darby, and Paul Maruff (of AUSTRALIA) for demonstrating that people make better decisions about some kinds of things — but worse decisions about other kinds of things‚ when they have a strong urge to urinate. REFERENCE: “Inhibitory Spillover: Increased Urination Urgency Facilitates Impulse Control in Unrelated Domains,” Mirjam A. Tuk, Debra Trampe and Luk Warlop, Psychological Science, vol. 22, no. 5, May 2011, pp. 627-633.

REFERENCE: “The Effect of Acute Increase in Urge to Void on Cognitive Function in Healthy Adults,” Matthew S. Lewis, Peter J. Snyder, Robert H. Pietrzak, David Darby, Robert A. Feldman, Paul T. Maruff, Neurology and Urodynamics, vol. 30, no. 1, January 2011, pp. 183-7.

ATTENDING THE CEREMONY: Mirjam Tuk, Luk Warlop, Peter Snyder, Robert Feldman, David Darb

Perhaps we need more (or is it less?) restrooms in the financial sector and Washington DC these days.

Energy unprincipled

I’ve been browsing the ALEC model legislation on ALECexposed, some of which infiltrated the Montana legislature. It’s discouragingly predictable stuff, but not without a bit of amusement. Take the ALEC Energy Principles:

Mission: To define a comprehensive strategy for energy security, production, and distribution in the states consistent with the Jeffersonian principles of free markets and federalism.

Except when authoritarian government is needed to stuff big infrastructure projects down the throats of unwilling private property owners:

Reliable electricity supply depends upon significant improvement of the transmission grid. Interstate and intrastate transmission siting authority and procedures must be addressed to facilitate the construction of needed new infrastructure.

Like free markets, federalism apparently has its limits:

Such plan shall only be approved by the commission if the expense of implementing such a plan is borne by the federal government.

The overconfidence of nuclear engineers

Rumors that the Fort Calhoun nuclear power station is subject to a media blackout appear to be overblown, given that the NRC is blogging the situation.

Apparently floodwaters at the plant were at 1006 feet ASL yesterday, which is a fair margin from the 1014 foot design standard for the plant. That margin might have been a lot less, if the NRC hadn’t cited the plant for design violations last year, which it estimated would lead to certain core damage at 1010 feet.

Still, engineers say things like this:

“We have much more safety measures in place than we actually need right now,” Jones continued. “Even if the water level did rise to 1014 feet above mean sea level, the plant is designed to handle that much water and beyond. We have additional steps we can take if we need them, but we don’t think we will. We feel we’re in good shape.” – suite101

The “and beyond” sounds like pure embellishment. The design flood elevation for the plant is 1014 feet. I’ve read some NRC documents on the plant, and there’s no other indication that higher design standards were used. Presumably there are safety margins in systems, but those are designed to offset unanticipated failures, e.g. from design deviations like those discovered by the NRC. Surely the risk of unanticipated problems would rise dramatically above the maximum anticipated flood level of 1014 feet.
Overconfidence is a major contributor to accidents in complex systems. How about a little humility?
Currently the Missouri River forecast is pretty flat, so hopefully we won’t test the limits of the plant design.