The figure below shows the distributions of answers to two Gallup surveys – taken in the years 1937 and 2007 – asking the respondents for the smallest amount of money a family of four would need each year to get along in their community.

The ratio between the median amounts is about 43,700 / 1,500 = 29. The increase in the official measure of the consumer price index for the period 1937 – 2007 is by a factor of 14.4.

In 2007 the median household income was $50,233. The median household income for 1935-1936 was about $1,068. The increase is about 47-fold. The income of the median income of a family of four increased from $3,292 in 1947 to $75,675 in 2007, an increase of about 23 times.

Data: Gallup questionnaire database: poll #84, question 4, 5/24/1937; question 8, SOCIAL SERIES WORLD AFFAIRS, 2/1-4/2007. The 1937 question was phrased in terms of weekly sum of money needed – the data was adjusted to give the yearly sum by multiplying by 365 / 7. Inflation calculator. Statistical Abstract of the US, 1940. Census bureau, historical income tables – Housholds. Census bureau, historical income tables – Families.

Distribution percentiles ($1000’s):

Percentile 10 20 30 40 50 60 70 80 90
1937 0.99 1.27 1.27 1.43 1.51 1.79 1.95 2.03 2.47
2007 24.5 29.75 34 39 43.75 49 55 57.5 77.5

Dishwashing: man vs. machine

September 24, 2008

When searching online for information comparing manual dishwashing to dishwashing machines, a University of Bonn study is the most prominent point of empirical research that shows up (e.g., 1, 2, 3, 4). This study is usually interpreted as showing that dishwashers are more resource efficient than hand washing – using less work time, less energy and less water to wash the same amount of dishes.

Some commenters in the Treehugger post linked above showed healthy skepticism of this all-too-convenient claim. Fortunately reports from the University of Bonn study are available online (1, 2, 3) and the researchers were kind enough to include some data in those reports, making it possible to examine the results rather than rely on media reports alone. I thus decided to have a methodical look at the study – this post presents my conclusions on this matter.


Multiple weaknesses in the experimental setup make the interpretation of the study difficult. The data analysis carried out by the researchers seems tendentious. Claims that the study shows that using a dishwashing machine saves substantial amounts of energy, water and time as compared to hand washing are highly dubious. According to the study’s own findings, the most efficient handwashers used far less energy (actually, none, since these washers used no hot water) and about the same amount of water as the most efficient machines. Using no hot water had no negative impact on the cleanliness of the washed dishes.

Read the rest of this entry »

Below is my page-by-page summary of Kuhn’s 1967 postscript to The Structure of Scientific Revolutions.

The following points seem to me to contain the essence of Kuhn’s thesis:


  1. Exemplars (solved problems) are an important component of any specific scientific world-view. Without exemplars the laws and theories have little empirical content. The exemplars teach practitioners how to attach the relevant abstractions to elements of particular problems and how to see a variety of situations as being alike.
  2. The intuitive knowledge of which situations are alike is analyzable but not by specifying rules since it is perceptual rather than interpretive knowledge. It is similar to other knowledge of perception: e.g., identifying certain light patterns as all representing swans. Perceptual knowledge is selected for “success” – success in survival in the primitive case, success in puzzle solving in the scientific case.
  3. The situation may be similar in non-scientific schools (e.g., art).


  1. Scientific revolutions – “a special sort of change in scientific thinking involving a certain sort of reconstruction of group commitments” – occur regularly on the smaller scale (within communities of dozens to hundreds).
  2. Crisis is the usual mechanism inducing revolutions. Crises supply a self-correcting mechanism which ensures that the rigidity of normal science will not forever go unchallenged.
  3. Judgments of scientific values – simplicity, consistency and compatibility – can vary greatly from individual to individual. Therefore, debates on theory-choice cannot be decided in a formal way. Still, those values constrain the dominant group view. This explains why competing world-views are rare in science but are common in other human activities.

Scientific progress:

  1. Because the commitment by scientists to puzzle-solving success shapes the long-term structure of scientific development (even if the application of this commitment in any particular case is ambiguous and subjective), scientific development, like biological development, is unidirectional and irreversible. When comparing scientific theories held by various scientific specialties to theories held by the specialty from which the former had their origins, “an uncommitted observer” would be able to consistently distinguish the newer theories from the older. The newer theories will enable more accurate, quantitative, predictions, in a wider variety of situations and they will be more esoteric. Differences in simplicity, scope and compatibility with other specialties are not as telling.
  2. Scientific progress is therefore well defined, but, like biological progress, it cannot be said that science comes closer and closer to a certain goal – “reality”. There is no objective reality which stands outside a specific scientific world-view.

Read the rest of this entry »