An Economic Assessment of Banana Genetic Improvement and ...

134 CHAPTER 9
Table 9.2 Summary statistics and hypothesized effects of variables
used in the analysis
Variable Description Mean
Standard
deviation
Dependent variables
Hybrid use Household grows a hybrid cultivar (yes = 1; no = 0) 0.19 0.39
Yield loss Average expected yield loss to joint biotic pressures
(percent)
4.23 7.31
Explanatory variables
Gender Gender of primary production decisionmaker (1 = male) 0.70 0.46
Education Average aggregate household education level (years of 6.30 1.98
schooling)
Experience Years of experience tending for the banana grove 20.57 13.87
Dependency ratio Ratio of children and elderly to active adult household 0.48 0.22
members
Extension Number of contacts with extension agents 1.63 4.01
Exogenous income Income received in previous period (ten thousand Tsh) 20.34 62.69
Livestock assets Value of total livestock assets (ten thousand Tsh) 20.28 43.92
Farm size Size of landholding (acres) 1.72 1.43
Elevation Elevation (stratification variable; 1 = low) 0.85 0.36
Probability BS Perceived frequency of occurrence of black Sigatoka disease 0.09 0.18
Probability FW Perceived frequency of occurrence of Fusarium wilt disease 0.23 0.23
Probability WE Perceived frequency of occurrence of weevils 0.34 0.28
of the landholding, another indicator of
wealth and the scale of production.
Exposure to banana hybrids and elevation
are two stratification variables. Only
elevation is included as an instrument in the
use equation, allowing for the identification
of the treatment effect in the impact equation.
The strength of the exposure variable
in capturing the effect of use of formally
distributed hybrids was compromised by
the markedly informal means of transfer of
planting material from one farmer to another
(this interpretation is supported by descriptive
information summarized in Chapter 5).
With as many as 20 percent of farmers in
nonexposed areas reported to grow banana
hybrids, the treatment effect of exposure
was dissipated. Geographical location is
believed to better explain use behavior, with
96 percent of households growing banana
hybrids (that is, 48 of the 50 households
using hybrids) residing in low-elevation
areas.
Determinants of Production
Vulnerability
Among the variables hypothesized to have
an effect on production vulnerability are the
acquired human capital variables and scale
of production (farm size). These characteristics
are intended to capture preferences for
management of the banana grove and scale
of production, which have implications for
yield loss, whereas the frequencies of occurrence
of the three biotic pressures reflect the
direct effects of disease and pest constraints
on production vulnerability. Production vulnerability
is also hypothesized to depend on
the use of banana hybrids. As hybrids are
bred for resistance to biotic pressures (in