title: Employment Growth in Italian Local Labour Systems: Issues of Model Specification and Sectoral Aggregation

authors: Mameli, Francesca

subjects: economic

abstract: In this paper we construct a model to estimate local employment growth in Italian local labour markets for the period 1991-2001. The model is constructed in a similar manner to the original models of Glaeser et al. (1992), Henderson et al. (1995) and Combes (2000). Our objective is to identify the extent to which the results estimated by these types of models are themselves sensitive to the model specification. In order to do this we extend the basic models by successively incorporating new explanatory variables into the model framework. In addition, and for the first time, we also estimate these same models at two different levels of sectoral aggregation, for the same spatial structure. Our results indicate that these models are highly sensitive to sectoral aggregation and classification and our results therefore strongly support the use of highly disaggregated data.

text: Employment Growth in Italian Local Labour Systems: Issues of Model Specification and Sectoral Aggregation In this paper we construct a model to estimate local employment growth in Italian local labour markets for the period 1991-2001. The model is constructed in a similar manner to the original models of Glaeser et al. (1992), Henderson et al. (1995) and Combes (2000). Our objective is to identify the extent to which the results estimated by these types of models are themselves sensitive to the model specification. In order to do this we extend the basic models by successively incorporating new explanatory variables into the model framework. In addition, and for the first time, we also estimate these same models at two different levels of sectoral aggregation, for the same spatial structure. Our results indicate that these models are highly sensitive to sectoral aggregation and classification and our results therefore strongly support the use of highly disaggregated data.

year: 2008

title: Estimating pre-historic earthquake parameters in the Hamilton lowlands using laboratory geotechnical analyses of seismically liquefied volcanic-ash layers in lakes

authors: Chaneva, Jordanka

abstract: Soft-sediment deformation structures caused by pre-historic earthquakes were discovered in volcanicash (tephra) units preserved as discrete layers within soft, organic lake sediments in the Hamilton lowlands, North Island, New Zealand. Complementing a broader paleoliquefaction project that involves geological and seismological perspectives as well, this PhD research was focused on a geotechnical approach in analysing the paleoliquefaction features in the tephra layers across multiple 20 cal-ka-aged lakes in the Hamilton lowlands. Aiming to back-analyse pre-historic earthquakes that might have caused the palaeoliquefaction features, this thesis also had to address literature and knowledge gaps related to cyclic undrained behaviour and liquefaction resistance of pumiceous silts and sand-silt mixtures. Thus, the scope of this research covered the following objectives: (1) analyses of the geotechnical properties of the tephras of interest in order to define their liquefaction susceptibility, (2) investigation of the undrained monotonic and cyclic behaviour of a pumiceous silt (Tuhua silt, from lacustrine Tuhua tephra aged 7.6 cal ka) in order to fill knowledge gaps related to potential particle crushing affecting undrained cyclic behaviour as well as liquefaction resistance in pumiceous silts, (3) identification of the potential threshold of pumice content and/or fines content, at which pumiceous sand-silt mixtures (internal beds from lacustrine Mamaku tephra aged 8.0 cal ka) become crushable, and finally (4) developing a framework, that extends laboratory obtained liquefaction resistance ratios of three different beds of one of the tephras of interest, that provided enough volume for cyclic undrained triaxial testing (Mamaku tephra), into the rest of the tephras across the studied lakes (that only provided small volumes for sampling). The last objective assisted in reaching the main aim of this thesis which was to obtain the equivalent triggering earthquake parameters, i.e., peak ground acceleration, amax and earthquake magnitude, M for the tephras across the lakes, based on their estimated liquefaction resistances. It was found that the tephras in the lakes are pumiceous and liquefiable within the grain-size range: silts to sandy silts to silty sands. The results from undrained triaxial testing on the pumiceous silt showed that no particle crushing occurred and that the silty material behaved closer to the typical trends established for hard-grained soils than to those associated with pumiceous sands. Furthermore, the undrained cyclic triaxial testing program on three different beds, one silt and two silty sands, from one of the tephras of interest (Mamaku tephra), suggested a fines threshold below which begin to crush during cyclic triaxial testing to be somewhere between 31% and 20%. Empirical correlations used to estimate earthquake parameters from liquefaction resistance that are derived for hard-grained soils were, thus, considered reasonable for application to the pumiceous materials considered in the current study. The final results of this study showed that the tephra layers across the lakes were very sensitive and vulnerable to liquefaction at very low peak ground accelerations, i.e. amax ranging from 0.02 to 0.08 g within the range of magnitudes, M = 5 to 8.5. The high vulnerability to liquefaction across all the Mamaku tephra layers in the Hamilton lowlands (~13 lakes) was considered to be the result of the very low in-situ overburden stresses, consequence of their shallow burial depths in the lake environment, as well as the relatively low liquefaction resistance in situ. The results presented in this dissertation, (1) supply valuable information about the liquefaction potential of pre-historically liquefied tephra layers, assisting local paleoliquefaction studies in the Hamilton lowlands area, (2) explore the possibility of applying laboratory-based liquefaction resistance analysis in paleoliquefaction studies, and (3) contribute to better understanding of the undrained behaviour and liquefaction resistance of pumiceous sand-silt mixtures.

text: Estimating pre-historic earthquake parameters in the Hamilton lowlands using laboratory geotechnical analyses of seismically liquefied volcanic-ash layers in lakes Soft-sediment deformation structures caused by pre-historic earthquakes were discovered in volcanicash (tephra) units preserved as discrete layers within soft, organic lake sediments in the Hamilton lowlands, North Island, New Zealand. Complementing a broader paleoliquefaction project that involves geological and seismological perspectives as well, this PhD research was focused on a geotechnical approach in analysing the paleoliquefaction features in the tephra layers across multiple 20 cal-ka-aged lakes in the Hamilton lowlands. Aiming to back-analyse pre-historic earthquakes that might have caused the palaeoliquefaction features, this thesis also had to address literature and knowledge gaps related to cyclic undrained behaviour and liquefaction resistance of pumiceous silts and sand-silt mixtures. Thus, the scope of this research covered the following objectives: (1) analyses of the geotechnical properties of the tephras of interest in order to define their liquefaction susceptibility, (2) investigation of the undrained monotonic and cyclic behaviour of a pumiceous silt (Tuhua silt, from lacustrine Tuhua tephra aged 7.6 cal ka) in order to fill knowledge gaps related to potential particle crushing affecting undrained cyclic behaviour as well as liquefaction resistance in pumiceous silts, (3) identification of the potential threshold of pumice content and/or fines content, at which pumiceous sand-silt mixtures (internal beds from lacustrine Mamaku tephra aged 8.0 cal ka) become crushable, and finally (4) developing a framework, that extends laboratory obtained liquefaction resistance ratios of three different beds of one of the tephras of interest, that provided enough volume for cyclic undrained triaxial testing (Mamaku tephra), into the rest of the tephras across the studied lakes (that only provided small volumes for sampling). The last objective assisted in reaching the main aim of this thesis which was to obtain the equivalent triggering earthquake parameters, i.e., peak ground acceleration, amax and earthquake magnitude, M for the tephras across the lakes, based on their estimated liquefaction resistances. It was found that the tephras in the lakes are pumiceous and liquefiable within the grain-size range: silts to sandy silts to silty sands. The results from undrained triaxial testing on the pumiceous silt showed that no particle crushing occurred and that the silty material behaved closer to the typical trends established for hard-grained soils than to those associated with pumiceous sands. Furthermore, the undrained cyclic triaxial testing program on three different beds, one silt and two silty sands, from one of the tephras of interest (Mamaku tephra), suggested a fines threshold below which begin to crush during cyclic triaxial testing to be somewhere between 31% and 20%. Empirical correlations used to estimate earthquake parameters from liquefaction resistance that are derived for hard-grained soils were, thus, considered reasonable for application to the pumiceous materials considered in the current study. The final results of this study showed that the tephra layers across the lakes were very sensitive and vulnerable to liquefaction at very low peak ground accelerations, i.e. amax ranging from 0.02 to 0.08 g within the range of magnitudes, M = 5 to 8.5. The high vulnerability to liquefaction across all the Mamaku tephra layers in the Hamilton lowlands (~13 lakes) was considered to be the result of the very low in-situ overburden stresses, consequence of their shallow burial depths in the lake environment, as well as the relatively low liquefaction resistance in situ. The results presented in this dissertation, (1) supply valuable information about the liquefaction potential of pre-historically liquefied tephra layers, assisting local paleoliquefaction studies in the Hamilton lowlands area, (2) explore the possibility of applying laboratory-based liquefaction resistance analysis in paleoliquefaction studies, and (3) contribute to better understanding of the undrained behaviour and liquefaction resistance of pumiceous sand-silt mixtures.

year: 2024

title: The Māori precariat: A silhouette

authors: Stubbs, Thomas

abstract: Recent financial crises and a host of punitive labour and welfare reforms have intensified socio-economic divisions across advanced nations. In Aotearoa New Zealand, the indigenous Maori peoples are subject to systemic labour market disadvantages, and are thus more likely to be affected by increased inequalities in times of economic downturn. Despite the legacies of systematic economic exclusion and discrimination in the economy, the majority of Maori demonstrate a resounding level of social resilience in the face of this hostile context. Even so, there is evidence to suggest that an unacceptable number of Maori still struggle to overcome these challenges. For instance, 13.0 per cent of Maori are in temporary work compared to 8.2 per cent of Pakeha,1 and 12.4 per cent of Maori are experiencing unemployment against 4.4 per cent. of Pakeha.2 These trends contribute to a range of socio-economic challenges, to which mainstream and Maori service providers are struggling to respond.
In this chapter, we develop a demographic silhouette to seek an understanding of socio-economically marginalised - or 'precariat' - Maori. Although we are wary of portraying Maori in an unduly negative light, we also submit that an appreciation of the extent of the issues faced by this group is necessary if our analysis is to be useful in the development of an effective response. We begin by defining the precariat. Using data obtained from Statistics New Zealand's Te Kupenga survey of Maori wellbeing, we then outline the prevalence and composition of the Maori precariat in Aotearoa New Zealand. Overall, we find that the Maori precariat comprises a substantial portion of the Maori population, particularly among females, younger age groups, and those with low or no qualifications. They are predominantly located-in regions that have high levels of seasonal employment, and in more deprived areas. We also find the value attached to Maori culture and experiences of stigma for this group are, for the most part, similar to those among the Maori non-precariat.

text: The Māori precariat: A silhouette Recent financial crises and a host of punitive labour and welfare reforms have intensified socio-economic divisions across advanced nations. In Aotearoa New Zealand, the indigenous Maori peoples are subject to systemic labour market disadvantages, and are thus more likely to be affected by increased inequalities in times of economic downturn. Despite the legacies of systematic economic exclusion and discrimination in the economy, the majority of Maori demonstrate a resounding level of social resilience in the face of this hostile context. Even so, there is evidence to suggest that an unacceptable number of Maori still struggle to overcome these challenges. For instance, 13.0 per cent of Maori are in temporary work compared to 8.2 per cent of Pakeha,1 and 12.4 per cent of Maori are experiencing unemployment against 4.4 per cent. of Pakeha.2 These trends contribute to a range of socio-economic challenges, to which mainstream and Maori service providers are struggling to respond.
In this chapter, we develop a demographic silhouette to seek an understanding of socio-economically marginalised - or 'precariat' - Maori. Although we are wary of portraying Maori in an unduly negative light, we also submit that an appreciation of the extent of the issues faced by this group is necessary if our analysis is to be useful in the development of an effective response. We begin by defining the precariat. Using data obtained from Statistics New Zealand's Te Kupenga survey of Maori wellbeing, we then outline the prevalence and composition of the Maori precariat in Aotearoa New Zealand. Overall, we find that the Maori precariat comprises a substantial portion of the Maori population, particularly among females, younger age groups, and those with low or no qualifications. They are predominantly located-in regions that have high levels of seasonal employment, and in more deprived areas. We also find the value attached to Maori culture and experiences of stigma for this group are, for the most part, similar to those among the Maori non-precariat.

year: 2017