Agriculture Reference
In-Depth Information
model the variance of the error term is set to one). Since we have data on
five time periods, and are lower-triangular matrices with size 5*5 and
have the following general shape:
Therefore, 16 unrestricted parameters are left in the model,
i.e.
eight parameters for both and The structure of these matrices is
general enough to control for firm specific individual effects and serial
correlation between the errors.
4. DATA
Data on specialised vegetables firms covering the period 1991-1995 are
obtained from a stratified sample of Dutch glasshouse firms keeping
accounts on behalf of the LEI accounting system. The panel is balanced
such that each firm is in the sample over the full five-year sampling period.
The data contain 450 observations on 90 firms.
Three heating technology choices
5
are distinguished,
i.e.
traditional
heating, traditional heating with energy storage, and co-generator with
energy storage. 345 observations (76%) use the traditional energy heating
technology, 39 observations (9%) use traditional heating combined with
energy storage in tanks and 66 observations (15%) use a co-generator with
energy storage.
Basic firm characteristics are capital invested in structures
(buildings, glasshouses, land and paving), capital invested in machinery
and installations, labour firm size and firm type. Labour is measured in
quality-corrected man years, and includes family as well as hired labour.
The quality correction on labour is performed by the Agricultural
Economics Research Institute, in order to aggregate labour from able
bodied adults with labour from young family members and labour from
partly disabled workers. Labour is assumed to be a fixed input in the short
term, because family labour represents a large share of total labour. Capital
in structures and machinery and installations is measured at constant 1985
prices and is valued in replacement costs. Firm size is measured in
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