About "Catch & Research"

Welcome. I found my passion in ecological economics and fishing. They are all about pursuit of unknown and uncertain objects. I always enjoy the seemingly reckless pursuit itself. This blog is a record of my long journey in research and fishing. Your comments are welcome and appreciated.

Monday, September 22, 2008

Silly error found at Structural Decomposition Analysis

Input-output structural decomposition analysis (SDA) using hybrid table is almost 20 years old and well known method in energy research field. This method was established by efforts from various scholars including S. Casler and A. Rose during the 90s. It has been broadly  used as a useful tool to measure sources of energy use change. There has not been much update of the method. 

Recently, I found one article which points out a silly and embarrassing error of SDA application: Dietzenbacher, E. & J. Stage. 2006. Mixing oil and water? Using hybrid input-output tables in a structural decomposition analysis. Economic systems research. 18(1):85-95.  The silly error is about unit problem at final demand decomposition: when units of energy or money changes, the results of level and mix effect change arbitrarily. For example, first I use million dollars for non-energy sectors and 10^15 Btus for energy sectors. Then I use the same million dollars for non-energy sectors but now 10^12 Btus for energy sectors. Now, I still get the same result for total final demand effect but totally different level and mix effects. 

They presented mathematical proof of the problem and also showed the results from SDA with two different units tables using data from the famous Miller and Blair text book (1985). At first time, I couldn't believe what they found. Because if it is true, then many previous literatures become questionable... I ran through many times over their findings and then finally couldn't but accept them. 
(Source: Dietzenbacher and Stage, p. 90. You can see level and mix effect are not consistent, although total effect does)

It is a major embarrassment in hybrid SDA. Monetary input-output analysis is utit-free. That must be one reason why no body has paid much attention on it. Who could have possibly  imagined this? The authors of this paper proposed two solutions to get rid of unit problems. I tested the solutions using data from Miller & Blair (1985) by myself and found that they seamlessly work without any unit problem. One question is economic meaning of the new decomposition sets. I need consider more about this.

I had chance to send email to the corresponding author, Dr. Jesper Stage to clarify some points in their paper. I complimented him that this paper seemed to be a classic in this field. Dr. Stage is a Swedish economist at University of Gothenburg. He had his master's degree in Physics. I thought that his background might help him to find this problem. At the end of his email, Dr. Stage emphasized that this finding does not weaken analytical power of hybrid power, although they found serious but solvable problem in "application" of SDA; hybrid SDA is a still useful tool.

My advisor has not been fully convinced by this paper. He encouraged me to write email to big names in this filed. So far, I am waiting for responses from Drs. Casler and Rose. I wonder what their reaction to the finding and their critique on the proposed solutions will be. 

Abstract of the paper;

Mixing Oil and Water? Using Hybrid Input-Output Tables in a Structural Decomposition Analysis


*Faculty of Economics, University of Groningen, The Netherlands, **Department of Economics, Umea° University, Sweden
(Received October 2003; revised September 2005)

Input-output studies of energy use frequently adopt the so-called hybrid table, where the rows corresponding to energy sectors are in energy units rather than in monetary units. However, we show that, in structural decomposition analyses, this hybrid approach may induce arbitrary results that depend on the choice of units, rather than on changes in economic structure. This is because an economically meaningless sum of monetary and energy units enters the calculations. Our proposed solution to this problem is based on using a sum of monetary units instead, thus avoiding this attempt to mix oil and water. 

KEY WORDS: Structural decomposition analysis, input-output analysis, energy use, hybrid input-output tables

Correspondence Address: Jesper Stage, Department of Economics, Umea° University, SE 901 87 Umea°, Sweden.
Email: Jesper.Stage@econ.umu.se

Friday, September 12, 2008

The 10 Biggest Myths in Bass Fishing

Fishing is definitely the art of experience. In general, angler who has the most experience rules. But in a new lake, everybody starts at the same line. It proves the level of an angler how one adapts oneself well to the new water. It must be the reason of the tournament rule that prohibits participating anglers from fishing during certain time before a tournament.

When one faces new water, troubles begin from one's experience. One may try everything to solve fishing equations of the day with one' s previous knowledge. Sometimes it works and sometimes not. It is difficult. Why is it so?

Current issue of In-Fisherman magazine points out that incorrect knowledge that most anglers believe true, or so called myths may be one reason of the difficulty. The virtue of the magazine is that it introduces academic findings not only story based on experience. There are couple more fishing magazines, but they seem not to cooperate with fishery researchers. Anyway, here is the 10 biggest myths in bass fishing (summary of article by Steve Quinn) :
  1. Bass become dormant it cold water
    During winter time, bass will be less active, but still do preying activities. "In north-east states, many of the biggest bass caught each year come through the ice." "Physiological models suggests that at 40 degree F bass need consume only about one third as much food to maintain nutrition as they do at 70 degree F. preyfish abundance is lowest in winter as well, But bass still eat."
  2. Bass strike red hooks because they resemble blood
    "Studies of bass vision indicate they detect red easily and can discriminate among shades. no research shows, however, any instinctive attraction to it." Bass don't have intelligence to conclude red color means bleeding prey.
  3. A bass is a bass...
    Do all bass have same life pattern? "Genetic studies show variation in the DNA of fish even from nearby watersheds within the same state. And differences in dies, water color and cover type also make bass from difference lakes behave differently."
  4. Modern livewells make fish care easy
    Anglers' ignorance and lack of care increase fish mortality even with modern livewells. "Anglers need to take measures to improve conditions: Run aerators constantly to add fresh water; add ice to lower livewell temperatures 5 degree F to 8 degree F; or run pure oxygen into the well" even they have modern livewells.
  5. You need a big, fast boat to fish efficiently
    "As in pas times, many of the best bass fishermen still use small, underpowered boats. Small boats are suited to small waters where giant bass dwell, from Florida to Iowa to California. Full-sized bass boats can't get into key shallow zones and have trouble maneuvering through dense timber or vegetation. When they do, the commotion often spooks lunkers." (My friend, Capt. M is a living proof of this. He uses kayak and canoe, but always outfishes.)
  6. Tournaments harm bass populations
    "A tagging study* found tournament mortality contributed from 1 to 16 percent of total annual mortality of the largemouth population, while non-tournament catch-and-release fishing were 2 to 17 percent of the total, and angler harvest (non-tournament) comprise 16 to 38 percent of annual bass mortality."
  7. Bass abandon areas treated with herbicides
    Lake manager sometimes use herbicides to treat over-grown water plants. "Excessively thick plant growth limits bass feeding and cuts the abundance of key preyfish like shat." (The author may mention about eutrophication.) "Scientific evidence suggests that bass are not negatively affected by correct application of herbicides"
  8. Big baits catch big bass
    "This myth isn't a fallacy. You can increase the average size of bass caught by using larger lures. But there's far more to that relationship." Small size bass will not hesitate to attack big baits also. According to finness fishermen, on the other hand, while food is scarce, big bass will be willing to attack tiny lures.
  9. Catching nesting bass is like picking cherries
    "Some anglers look down on sight-fishing for bedding bass as unsporting and unethical, in that it takes advantage of bass at their most vulnerable moments." However, it could be very easy or almost impossible to catch.
  10. Stocking Florida bass improves lunker catches
    "Introduction of Florida bass into California has resulted in the biggest bass on the planet. In more temperate locations, however, this can lead to downturn in fishing"

More myths:

  • Planting brushpiles increases bass populations
    "In most cases, brush and other attractors concentrate bass but do little to enhance reproduction, lake-wide biomass, or growth." "Effect (of planting brushpiles) are local, not population-wide
  • Big bass live in deep water
    "Big bass live where living conditions an prey availability support their bulk. That can be shallow, deep, or in between, depending on available habitat and type." "Tacking studies have shown that some big bass hold on deep structure during the day but move into the 10-foot zone to feed after dark. In deep, clear lakes, lunkers may hold in open water, but they're often suspended at levels where baitfish are most available."
  • Bass seek crayfish in Spring for nutrition benefits
    "Creyfish are rather poor food from the stand point of nutrition." "Low fat content and caloric value also make craws less nutritious than most fish. But they're easy to find and catch, particularly in spring when weedgrowth is thin."

Friday, September 5, 2008

Meeting with advisor (9/5): SDA equations

I asked my advisor about which way of decomposition I should use? There are many ways of decomposition. For example, total energy use can be decomposed to as simple as final demand change effect + input requirement change effect + joint effect. Or it can be decomposed to much complex equations including capital, labor, material substitution effects. Or it can be decomposed including effects from trade. It really confuses me. Which way is better to explain my topic? His advice was to start with the simplest one, then add more decomposition equations. Right, I have to start, although I don't have a perfect blueprint.

Observation of conventions

US presidential election race is heating up. In the desperate hope that we can beat the war criminal, George W Bush at this time, I am watching carefully the race. I watched national conventions of two parties. Here is key words that summarize my observation of the two conventions.

Democratic National Convention

  • Party! (literally)
  • American Dream and Promise
  • Party unity
  • Hillary, the big-heart
  • Kennedy, the legend
  • Yes, we can!
  • Change
  • Diverse delegates
  • Universal health care
  • What we can do for unprivilaged people?

Republican National Convention

  • Fight, fight, fight
  • Jerry Springer family of vice president candidate
  • Desperate house wife or Pit bull
  • McCain, the lost
  • Another Bush
  • Grandpa, grandma delegates
  • No African-, Asian- American delegates
  • RNC Definition of American= White, old & rich people
  • Anti-war protests outside RNC
  • How to protect our own interest?

In particular, the surprise pick of Republican vice president really entertained me. I didn't think that this kind of drama was possible in the US; I have seen many in Korea. John McCain must need shockers to revive his dying out campaign. But this package was too much.

Yes, you can call me democrat. I would be happy to be branded that way if I can punish the war criminal. Dear American friends, you should know that how this president deceived you to the unjustified war, and you have to change it.