D5 Annex report WP 3: ETIS Database methodology ... - ETIS plus

D5 Annex WP 3: DATABASE METHODOLOGY AND DATABASE USER
MANUAL – FREIGHT TRANSPORT DEMAND
For example:
Orig/ Dest Dest1 Dest2 Dest3 Total
Orig1 100
Orig2 200
Orig3 300
Total 150 250 200 600
For this study, the problem can be seen as a series of large matrices, one for each commodity.
The origins and destinations are a mixture of countries and regions. Country to/from country
and country to/from region flows will be known, but subsets of the matrices will appear as
above, e.g. France to/from Spain.
For example, Iron and Steel Trade,
Orig/ Dest Champagne Picardie Hte Normandie Total
Galicia 100
Asturias 200
Cantabria 300
Total 150 250 200 600
There are various iterative procedures for finding "solutions" to these problems, but these are
essentially computer algorithms that have too many degrees of freedom to reach conclusive
results. They fit but they are not necessarily right.
It is possible to "seed" the matrix by filling it with particular values before the iteration solves it.
The seeding biases the results, so if the seeding is performed according to a valid theory of what
the matrix represents, it should improve the result.
One possibility is the so­called "Gravity Model" which takes into account the distance between
any two regions in the matrix. By introducing seeded values inversely proportional to the
distance (interpreted as the attraction between cells) between the regions it ought to be possible
to improve accuracy. Further accuracy might be achieved by extending the analysis to using
Generalised Cost instead of pure distance, and other factors such as language compatibility,
common currency, joint membership of trade bloc, and so on.
Many sophisticated procedures can be hypothesized, but without any base matrices to test the
results against, it is difficult to judge their validity. In these circumstances, if the base matrix
were known, there would be no practical reason for trying to estimate it. This is the problem.
Document2
27 May 2004
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