285
15 The Damage Schedule Approach
in order to decide which of the two objects is preferable” (David 1988 , 1). Initially
employed in psychometry (e.g. Thurstone 1927 ) , its fi elds of application have more
recently been expanded to include, among others, acoustics, animal ecology, economics,
epidemiology, food science and sports. Furthermore, its use in eliciting public preferences and judgments in an environmental study setting has been justi fi ed by a
number of studies that employed this method with a similar intention (Peterson and
Brown 1998 ; Rutherford et al. 1998 ; Chuenpagdee et al. 2001 ; Rudd 2001 ; Wattage
and Mardle 2005 ; Quah et al. 2006 ) . The method begins by establishing a set of
objects under the theme of a particular study, whether it is resource losses, damaging activities or community programs. The objects are presented in pairs to each
respondent, who then is asked to make a choice between them. This will continue
one after another until all possible pairs are exhausted. Standard notation denotes N
as the total number of objects, while the total number of respondents are denoted as
k . For each respondent, the total number of all possible pairs for comparison is N
( N -1)/2. Under normal circumstances, each object has the same probability of being
selected as all objects are paired an equal number of times.
There are at least three key advantages of using paired comparisons. First, a fi ne
judgment can be better achieved in a binary setting, especially when objects are
deemed to have subtle differences. The usual dif fi culty that faces a simultaneous
ordinal ranking of all N objects can be lessened. Secondly, the paired comparison
method can be used to produce an interval scale in which the numerical differences
between the objects have an arithmetic meaning. It shows the spread of the objects
on a scale, and is useful in explaining the extent to which one object is preferred
over others in numerical terms. The third advantage of the paired comparison exercise is that it is simple to conduct, and thus can be repeated or modi fi ed to accommodate changes in the systems that we are interested in. An obvious drawback of
the approach is the limited number of objects that can be included in the comparison, at least in the complete design. When the number of pairs presented is too large,
respondents may become fatigued and tend to believe that there are repetitive pairs,
even if there were not.
Case Study: Southeast Arm Fishery in Lake Malawi
Like many fi sheries around the world, illegal fi shing is widespread in Lake Malawi.
Towards the southeastern area called the Southeast Arm (SEA), illegal fi shing is
thought to contribute signi fi cantly to species decline, adding to existing concerns
over stock depletion, as well as the loss of livelihood opportunities and sources of
animal protein (Banda et al. 2005 ; Bulirani 2005 ) . The concept of illegal fi shing fi rst
became a topic of importance in Lake Malawi in the 1930s. British colonial conservationists, concerned with the lake’s ecology and fi sh conservation, indignantly
viewed traditional fi shing methods, such as weirs and traps, as destructive and primitive. Determined to restrict these traditional practices, they introduced a series of
early fi shing regulations (Chirwa 1996 ) . Through the establishment of the Department
15 The Damage Schedule Approach
in order to decide which of the two objects is preferable” (David 1988 , 1). Initially
employed in psychometry (e.g. Thurstone 1927 ) , its fi elds of application have more
recently been expanded to include, among others, acoustics, animal ecology, economics,
epidemiology, food science and sports. Furthermore, its use in eliciting public preferences and judgments in an environmental study setting has been justi fi ed by a
number of studies that employed this method with a similar intention (Peterson and
Brown 1998 ; Rutherford et al. 1998 ; Chuenpagdee et al. 2001 ; Rudd 2001 ; Wattage
and Mardle 2005 ; Quah et al. 2006 ) . The method begins by establishing a set of
objects under the theme of a particular study, whether it is resource losses, damaging activities or community programs. The objects are presented in pairs to each
respondent, who then is asked to make a choice between them. This will continue
one after another until all possible pairs are exhausted. Standard notation denotes N
as the total number of objects, while the total number of respondents are denoted as
k . For each respondent, the total number of all possible pairs for comparison is N
( N -1)/2. Under normal circumstances, each object has the same probability of being
selected as all objects are paired an equal number of times.
There are at least three key advantages of using paired comparisons. First, a fi ne
judgment can be better achieved in a binary setting, especially when objects are
deemed to have subtle differences. The usual dif fi culty that faces a simultaneous
ordinal ranking of all N objects can be lessened. Secondly, the paired comparison
method can be used to produce an interval scale in which the numerical differences
between the objects have an arithmetic meaning. It shows the spread of the objects
on a scale, and is useful in explaining the extent to which one object is preferred
over others in numerical terms. The third advantage of the paired comparison exercise is that it is simple to conduct, and thus can be repeated or modi fi ed to accommodate changes in the systems that we are interested in. An obvious drawback of
the approach is the limited number of objects that can be included in the comparison, at least in the complete design. When the number of pairs presented is too large,
respondents may become fatigued and tend to believe that there are repetitive pairs,
even if there were not.
Case Study: Southeast Arm Fishery in Lake Malawi
Like many fi sheries around the world, illegal fi shing is widespread in Lake Malawi.
Towards the southeastern area called the Southeast Arm (SEA), illegal fi shing is
thought to contribute signi fi cantly to species decline, adding to existing concerns
over stock depletion, as well as the loss of livelihood opportunities and sources of
animal protein (Banda et al. 2005 ; Bulirani 2005 ) . The concept of illegal fi shing fi rst
became a topic of importance in Lake Malawi in the 1930s. British colonial conservationists, concerned with the lake’s ecology and fi sh conservation, indignantly
viewed traditional fi shing methods, such as weirs and traps, as destructive and primitive. Determined to restrict these traditional practices, they introduced a series of
early fi shing regulations (Chirwa 1996 ) . Through the establishment of the Department