Urban Shrinkage Research Articles

Determining the effects of green space usage on health inequalities among residents of shrinking cities based on a social capital perspective

Long-term population loss and economic downturns have led to shrinking cities generally lacking social vitality and losing public spaces, such as green spaces. Previous studies have demonstrated the importance of green spaces for the social capital and health of residents, but the impacts of green space usage on health inequalities in the context of urban shrinkage have not been fully explored. In addition, residents who live in shrinking cities in northeastern China are more likely to suffer health problems due to their location in a severely cold region. Therefore, we selected 17 urban green spaces in Hegang, a typical shrinking city, as the research objects. We collected a total of 544 valid questionnaires through random distribution. These data were used to evaluate four green space usage characteristics of residents comprising transportation costs, usage frequency, usage duration, and participation in activities, as well as two social capital dimensions that are directly related to health comprising social networks and reciprocity and trust. We conducted correlation analysis, multivariate analysis of variance, and analysis of covariance to explore the impacts of green space usage on two categories of social capital for residents with different attributes and the consequences of health inequalities. The results showed that: (1) women, middle-aged and elderly people, and the low- and middle-income classes were less able to access social capital through the usage of green spaces; (2) the frequency of green space usage and intensity of participation in social activities were key dimensions that affected inequality; and (3) the usage of green spaces reinforced inequalities in the level of reciprocity and trust among residents. Based on our findings, we recommend that local governments in shrinking cities pay more attention to green spaces and squares in inner city areas to improve the accessibility and usability of these open spaces. Governments should focus on regenerating green spaces located near older neighborhoods to increase opportunities for residents to make new social connections and reduce inequalities in public services and health, especially for improving the social well-being of older populations with a lower socioeconomic status.

Recent Dynamics of Suburban Advancement and Building Densification in Relation to Landslide Exposure in the Main Cities of North-East Romania

We live in a complex and highly dynamic risk society, and given the massive environmental changes, exposure to hazards has become a critical concept that is part of all risk assessments made from a spatial perspective. In urban studies, evaluating exposure to different risk phenomena influences targeted policies and planning that can shape cities while making them safer. As in other post-socialist countries, in Romania, cities have had a highly divergent recent evolution, including processes such as urban shrinkage, the suburban advancement of cities, and urban sprawl. Focusing on seven cities from the North-East Region of Romania, the current paper is an exploratory study regarding the dynamics of exposure to landslides in relation to suburban advancement and densification of cities. Using the official statistics, available GIS databases and information based on satellite images illustrating urban land use changes in the last 20 years, the paper includes a general overview of the overall evolution of urban areas against landslide probability, followed by a more in-depth assessment of specific areas that were subject to functional change and currently include buildings that are susceptible to be affected by landslides. The results and conclusions converge towards the idea that the identified exposed areas, where actual ground movements are currently registered, need special attention from experts and authorities to identify and manage risks. The significance of our findings is underscored by their potential to inform and guide more effective territorial management and urban land use planning strategies.

Research on spatiotemporal patterns and influencing factors of county-level urban shrinkage in urbanizing China

County-level cities, as small-scale urban units in China's urban system, have shrunk due to uneven urban development in urbanizing China. This research constructed a framework for understanding China's county-level urban shrinkage. It defined county-level cities and measured shrinkage using the city shrinkage model, explored the spatiotemporal patterns combined with shrinking degrees and trajectories, and analysed the shrinking types based on city and city periphery perspectives. Then, the influencing factors were identified via the OLS regression model. Taking 2846 county-level cities as research units, the results showed that 180 and 1050 county-level cities shrunk in 2000–2010 and 2010–2020, respectively. Slight and moderate shrinkage dominated, but the proportions of high and severe shrinkage noticeably increased. In terms of shrinking trajectory, recent shrinkage was the main shrinking type. The spatial extent of shrinking county-level cities increased dynamically; the northeast, north, central and northwest regions were core agglomerations, and the east region emerged as an added agglomeration during 2010–2020. Absolute shrinkage became the main shrinking type significantly driven by "city–city" and "off-site urbanization" migration. Urbanization level, economic development, ageing degree, etc., were factors causing shrinkage. This study contributes to advancing understanding among scholars and Chinese policymakers about county-level urban shrinkage in urbanizing China.

Smart adaptation to urban shrinkage in North Gyeongsang province, South Korea: opportunities and obstacles for implementation

ABSTRACT In shrinking cities, adaptive responses such as ‘smart shrinkage’ are regarded as a promising approach to address depopulation and the quality of life for remaining residents. While its validity gains recognition, the gap between theory and practice still exists. Empirical studies validating the theoretical concept are few, particularly in the context of Asia where urban shrinkage is rapidly occurring. This study identified key opportunities and obstacles for realizing adaptive responses in practice, using the case of North Gyeongsang Province, South Korea. The findings showed that its adaptive responses were complementary to pro-growth responses, strengthening regional relationships and shared infrastructure.

Smart Growth and Smart Shrinkage: A Comparative Review for Advancing Urban Sustainability

In the context of ongoing global urbanization, the disparity in urban development, marked by the dual phenomena of urban sprawl and urban shrinkage at the regional level, has become increasingly evident. In this vein, two land-related governance strategies—smart growth (SG) and smart shrinkage (SS)—emerge as potential remedies to these challenges, targeting urban expansion and shrinkage, respectively. This study bridges the gap in the fragmented discourse surrounding SG and SS by conducting a comprehensive comparative review on the respective literatures. Utilizing the Scopus database, our research employs trend analysis, text and topic mining, time node analysis, and regional analysis, augmented by qualitative reviews of seminal papers. The findings reveal a notable shift in research focus, with interest in SS surging around 2010 (the number of SS-related papers published after 2010 accounts for 92.3% of the total number of the entire study period) as attention to SG waned, suggesting an impending paradigm shift in urban sustainability. The analysis indicates that SS research lacks the disciplinary diversity, thematic breadth, and empirical depth of SG studies, underscoring a need for a more robust theoretical foundation to support urban sustainability. Furthermore, while both SG and SS derive from environmental science foundations, SG predominantly addresses the physical and landscape attributes of urban areas, whereas SS focuses more on socio-economic dimensions. Our findings point to an intrinsic link between SG and SS, which could lay the groundwork for their integration into a unified theoretical framework to better advance urban sustainability.

Does Reduced Space Result in Fewer Rights? Controlled Shrinking in the Urban Renewal of Genoa

This article explores three examples of urban design initiatives in Genoa in an attempt to highlight the potential and possible contradictions that controlled shrinking projects pose for the future of contemporary cities. Genoa, a symbol of Italian shrinking cities, has been strongly defined over the years by post-industrialisation transformations and by long-standing conditions of urban shrinkage. Despite facing continuous shrinkage, local urban development policies have historically focused exclusively on urban growth and expansion. Only recently have some areas in Genoa started to adopt spatial planning experiences that actively pursue degrowth policies, aiming to reduce existing urban fabric and decrease urban density. These initiatives are adopted in specific areas affected by demographic decline, hydrogeological risks, pollution, or catastrophic events. These spatial strategies justify their existence by invoking concepts like smart shrinkage and degrowth, promising improvements in both environmental and social conditions. However, this article notes how these concepts in Genoa are not aligned with the actual social and environmental challenges that these considerations and positions pose. In fact, the urban renewal initiatives introduced by institutions, in reality, lean towards a strategy of shrinkage and demolition of residential complexes, transportation infrastructure, and productive spaces, with diverse and conflicting results. The observed controlled shrinking projects neglect the synthesis of the territory as a palimpsest, ignore new ecological sensitivities, and lack awareness of the social implications associated with the concepts of smart shrinkage and degrowth. Instead, the three instances introduce a spatial project that still adheres to the underlying principles of growth and exploitation, presenting a shrinkage of the existing urban fabric that is mere illusion. It involves clearing out the deteriorated spaces only to fill them with capitalist rhetoric and models that, instead of creating space, undermine fundamental rights. Nonetheless, a closer examination of these three missed opportunities sheds light on the necessary knowledge, actions, and design approaches for a city to navigate urban shrinkage adeptly. This exploration also reveals the potential for the city to transform into a framework and platform, inspiring and guiding new urban planning paradigms for sustainable development.

Evaluating urban development in China's resource-based cities: a new perspective using nighttime light data

ABSTRACT Understanding the urbanization and transformation trajectories of resource-based cities (RBCs) is pivotal for China’s sustainable development goals. This study introduces a novel regression-based algorithm for assessing urbanization patterns. We delineated the urban boundaries of 335 cities and employed time-series nighttime light data from 2001 to 2020, shifting the analysis from a pixel-scale to an urban-scale perspective. Our analysis reveals distinct disparities within the 125 RBCs when compared to the national average, leading to their categorization. The key findings include: (1) Within Forest and Coal RBCs, numerous areas have stabilized after experiencing contraction. Geographically, a significant number of RBCs in the Northeast, North, and Northwest regions are experiencing or have experienced substantial urban shrinkage. The developmental status of RBCs exhibits a spatial positive correlation. (2) Although the government categorized RBCs based on their development level in 2013, findings suggest that this classification may no longer accurately reflect the current development status of RBCs in the context of urbanization. (3) Utilizing spectral clustering, we categorized RBCs into five types, identified 10 RBCs undergoing shrinkage and 30 cities trending towards stabilization post-shrinkage. This research offers a refined evaluative method for urbanization, providing insights beneficial for policy-making concerning RBCs’ sustainable growth..

Shrinking Cities for Economic Growth? Insights From the Housing Sector

This research focuses on examining how the pursuit of economic growth can contribute to urban shrinkage. In contrast to the prevalent definition of urban shrinkage that links population loss to insufficient levels of economic growth, this study examines the case of Coimbra, Portugal, where something different is happening. We hypothesise that Coimbra experiences population loss due to urban policies that promote economic growth through housing speculation. We conclude that the hypothesis is valid using semi-structured interviews and document analysis as data collection methods. The identified phenomenon disproportionately affects younger and vulnerable residents, forcing them to relocate due to unaffordable housing options. However, it benefits the local authority and national government, which collaborate with global economic powers that invest in real estate to accumulate capital. The conformist and legalistic-bureaucratic nature of the Portuguese planning system, evident in Coimbra’s local authority, exacerbates the problem. We emphasise the potentially transformative impact of economic degrowth thinking on housing policy. The implications of this research question the validity of mainstream economic theory as commonly applied to urban planning.

Regrowth or smart decline? A policy response to shrinking cities based on a resilience perspective

Enhancing urban resilience is increasingly crucial for cities to achieve sustainable development. However, existing studies have a limited understanding of the resilience of shrinking cities and their response policies. Taking Yichun, a typical shrinking city in China, as an example, this study constructs a system dynamics model to assess urban resilience from a subsystem perspective and explores the relationship between the dynamic development of resilience and urban shrinkage from 2008 to 2028. Then, a smart decline response policy of Yichun is put forward. The findings indicate that the evolution curve of urban resilience shows a fluctuating growth trend as a whole and that the dominant subsystems of resilience are changing. The occurrence of urban shrinkage inhibits the dynamic development of urban resilience and has various effects on the subsystems of resilience. Compared with the regrowth strategy, the smart decline strategy can effectively improve the resilience and mitigate the adverse impact of urban shrinkage on the resilience under the condition of limited resources. Resilience can be proven to be a viable perspective to help formulate a response strategy of shrinking cities. These findings will enhance comprehension of the resilience of shrinking cities and provide a reference to address urban shrinkage and formulate corresponding governance strategies.

How studentification reshapes social vulnerability in urban Korea: Impressions based on regeneration and shrinkage

This work examines to what degree studentification may be associated with social vulnerability and be influenced by urban regeneration and shrinkage across four anchor institutions and their surrounding areas. Focusing on four South Korean metropolitan cities and utilizing longitudinal secondary data concerning studentification, social vulnerability, and shrinkage, we conducted correlation analysis and comparative case studies. Our findings demonstrate that each campus and surrounding areas reflected distinct urban phenomenon, particularly in terms of the relationships among studentification, social vulnerability, urban shrinkage, and urban regeneration. Of notable concern, student influx (as a representative studentification outcome) was determined to be a driver in influencing lower social vulnerability and less shrinkage. In this vein, our study provides initial insights for policymakers and urban residents in potentially addressing urban challenges and studentification in combination with urban regeneration and shrinkage.

Research Progress and Prospects of Shrinking Cities

This Amidst the wave of globalization and urbanization, the phenomenon of urban shrinkage is gradually becoming a "new normal" in urban development, triggering a series of profound questions regarding urban sustainability. With profound changes in the domestic and international socio-economic environment, the phenomenon of urban shrinkage has also begun to emerge in some cities and regions in China, posing a severe challenge in the process of new urbanization. This phenomenon not only challenges the traditional concepts of urban planning and management, but also prompts scholars in the field of economic geography to re-examine and conduct further research. This article aims to summarize the latest progress in the study of shrinking cities, delve into their connotation, identification criteria and type classification, underlying causes and mechanisms, as well as coping strategies. By doing so, we hope to provide theoretical support and practical guidance for the research and practice of urban shrinkage issues in China, and promote sustainable urban development and modernization of governance.

Urban Shrinkage from the Perspective of Economic Resilience and Population Change: A Case Study of the Shanxi-Shaanxi-Inner Mongolia Region

With the increasing uncertainty of urban development, urban shrinkage in the rapid urbanization process in China has become increasingly serious. While many studies have explored urban shrinkage from the economic and population perspectives, they often ignore the essence of the phased evolution of economic and population factors. Thus, this study introduces the theory of economic resilience into the field of urban shrinkage and constructs a theoretical method for identifying urban shrinkage by integrating economic resilience and population change to reveal the evolutionary trajectory of regional urban growth and shrinkage. The results show that urban economic resilience and population change in the Shanxi-Shaanxi-Inner Mongolia region (SSIMR) exhibit strong volatility, highlighting the importance of conducting urban shrinkage studies within specific crisis disturbance scenarios. In the context of the “new normal of the economy”, the economic resilience of cities in the SSIMR has significantly declined, and the problem of economic recession is gradually intensifying. The population change trend of cities in the SSIMR is relatively stable, with population loss being a common problem in urban development in the area and its scope and intensity increasing daily. Urban development in the SSIMR is evolving from global growth to widespread shrinkage, with 56.67% of the cities experiencing relative shrinkage, showing a spatial pattern of “western growth–eastern shrinkage”. Factors such as the agglomeration effect, industrial structure, and policy system collectively shape the evolution of urban growth and shrinkage.

Technology Finance and Urban Development: A Quantitative Approach to Shaping a New Future for Shrinking Cities

Using a dataset of 30 cities of different administrative levels in Liaoning Province, China, for the period 2007-2020, this study proposes a novel quantitative methodology for assessing the impact of socio-economic factors on the attractiveness of shrinking cities. By combining a shrinkage model with principal component analysis and extreme value normalisation of key indicators such as population size, GDP, retail sales of consumer goods, public budget expenditure, and secondary and tertiary employment, we provide a detailed analysis of the phenomenon of shrinking cities and its drivers. Using an interdisciplinary approach involving economics, psychology and sociology, we redefine traditional indicators for assessing the attractiveness of cities by analogising urban population dynamics to the process of molecular transfer in physical chemistry. This approach allows us to quantify the attractiveness of cities in four ways: socio-economic attractiveness, cost of living, public services and employment opportunities. The case study of Fushun illustrates the application of our model, revealing the potential for negative attractiveness across all dimensions and highlighting the multifaceted challenges facing shrinking cities. Our findings highlight the critical role of balanced socio-economic development, well-developed public services, affordable living conditions and adequate employment opportunities in enhancing the attractiveness of cities. This comprehensive framework provides valuable insights for urban planners and policymakers aiming to mitigate urban shrinkage and promote sustainable urban development.

Spatial and temporal evolution of habitat quality and its shrinkage effect in shrinking cities: Evidence from Northeast China

Continued population loss in the context of urban shrinkage has led to the transformation and reconfiguration of urban land use space, which in turn has had a major impact on regional habitats and ecosystem services. To explore the status of habitat quality (HQ) in shrinking cities, based on land use data from 2010 to 2020, this study uses the InVEST model to analyze the spatiotemporal characteristics of HQ in shrinking cities. Then, we reveal the shrinkage effect of HQ in shrinking cities from the perspective of population change rate, and detect the dominant influencing factors of HQ in different types of shrinking cities with the help of geographical detector. The results show that:(1) From 2010 to 2020, the primary land use types in both shrinking and non-shrinking cities of the three northeastern provinces were forestland and cropland. However, there were significant differences in the area of construction land between the two categories of cities. (2) The HQ in both shrinking and non-shrinking cities showed a declining trend, yet the HQ index of shrinking cities was higher than that of non-shrinking cities. (3) The distribution of HQ in shrinking cities has a significant shrinkage effect, and HQ index gradually strengthens as urban shrinkage intensifies. Low-quality habitats have a strong distributional advantage in slightly shrinking cities, while severely shrinking cities tend to be dominated by high-quality habitats. (4) Population profile, economic development, industrial structure and built environment are important factors influencing the spatial heterogeneity of HQ in shrinking cities. However, the spatial determinants of HQ vary significantly among different types of shrinking cities in terms of dimensions and indicators, with two-factor interactions exerting a stronger influence than single-factor impacts. Based on the findings of this study, the government can formulate differentiated habitat protection measures, dynamically adjust, and optimize them according to the distribution characteristics of HQ grades in shrinking cities.

Cities’ Hands Are Tied: Short-Term Economic Impacts of COVID-19 on Natural Population Growth in Metropolitan Greece

To delineate new directions of urban development in a context of demographic shrinkage in Southern Europe, the present study illustrates a comparative analysis of the demographic balance in metropolitan Athens, Greece (1956–2021). The analysis delineates short-term and long-term dynamics of the natural population balance, considering the impact of the Great Recession and COVID-19 pandemic, and assuming a contemporary increase in gross mortality rates and a marked fertility reduction associated with birth postponement. To address such objectives, we have compared the natural growth of population (the ratio of the total number of births to deaths) at ten year intervals (1956, 1960, 1970, 1980, 1990, 2000, 2009, 2019, 2020, 2021) in 115 municipalities of metropolitan Athens, controlling for the local context. The empirical results of descriptive statistics, spatial analysis, correlation statistics, non-parametric inference, and exploratory multivariate techniques outline the indirect impact of COVID-19 on population dynamics, being in some ways additive to the already observed effects of the Great Recession, reinforcing demographic shrinkage in specific local contexts. The COVID-19 pandemic and the Great Crisis likely accelerated the typical outcomes (population aging and low fertility) of the second demographic transition in Greece. These dynamics are associated with more volatile (and possibly reduced) immigration flows and with enhanced emigration, fueling urban shrinkage and a progressive economic decline of metropolitan regions, as our evidence suggests for Athens. Additional research should ascertain the aggregate, indirect role of pandemics in population dynamics as a proxy of urban and regional decline in European regions exposed to long-term aging.

Recognizing urban shrinkage and growth patterns from a global perspective

The incongruous patterns of urban growth often give rise to a myriad of issues, notably urban sprawl and urban shrinkage. These challenges frequently coexist and interact, presenting formidable obstacles to achieving sustainable city development. Therefore, investigations that endeavor to scrutinize both urban expansion and shrinkage in concert from a comprehensive perspective are essential. Present works of defining this trajectory are still vague, in which there is no clear clarification, and the relationship with socioeconomic also tends to be neglected. Thus, we proposed a new framework utilizing characteristic changes over 30 years in population and density to conduct a synthesis of urban growth patterns in 3911 cities worldwide along with their driving factors. We found that the development stage played a crucial role in urban growth pattern. Specifically, the densification cities were mostly found in the early stages of industrialization and urbanization. However, in accelerated industrialization and fast-developing regions, sprawl cities progressively gained dominance. Most cities followed the sprawl pattern and more shrinkage cities began to emerge in regions which in post-industrialization developed at high stages. Factors including industrialization level, urbanization rate, initial population density, terrain, and cultivated land conditions all exerted notable influences revolving around the urban growth process. Our study aims to help gain an overall sense of the global urbanization process as well as guide decision-makers to search for tailor-made management policies and urban planning for cities at various development stages. The patterns of expansion and shrinkage could offer support for a more comprehensive assessment of SDG indicators 11.3.1 and thus inform policies for urban sustainable development.

Contrary to expectation: The surface urban heat island intensity is increasing in population shrinking region while decreasing in population growing region-A comparative analysis from China.

Exploring the complex relationship between population change and surface urban heat island (SUHI) effect has important practical significance for the ecological transformation development of shrinking cities in the context of the prevalence of urban shrinkage and the global climate change. This paper compares the population change and SUHI effect between population shrinking region (Northeast Region, NR) and population growing region (Yangtze River Delta, YRD) in China, and explores their differences in driving mechanisms, using GIS spatial analysis and Geodetector model. Our results indicated that there are significant differences in population changes and SUHI intensity between these two regions. About 72.22% of the cities in the NR were shrinking, while their SUHI intensities increased by an average of 1.69°C. On the contrary, the urban population in the YRD shows a linear growth trend, while their SUHI intensities decreased by 0.11°C on average. The results of bivariate Moran's I index also indicated that the spatial correlation between the urban population changes and the SUHI intensity changes are not significant in the above regions. Furthermore, there are significant differences in the primary drivers of SUHI variations between these two regions. In the NR, underlying surface changes, including the changes of green coverage and built-up areas, are the most important driving factors. However, atmospheric environment changes, such as carbon dioxide emission and sulfur dioxide emission, are the key drivers in the YRD. Northam's theory of three-stage urbanization and environmental Kuznets curve hypothesis are powerful to explain these differences.

Understanding urban expansion and shrinkage via green plastic cover mapping based on GEE cloud platform: A case study of Shandong, China

Green Plastic Cover (GPC) has been widely used in construction sites of China as the main measure for dust suppression. As a unique land cover in China, GPC could be viewed as a sign for evaluating the intensity of urban construction. Therefore, time series GPC maps could provide a new perspective to understand the pattern of urban development, including both urban expansion and urban shrinkage. The objective of this study is to present a novel framework for detection of urban development patterns based on high resolution GPC maps generated from Google Earth Engine (GEE) cloud platform. Specifically, we first generated the GPC maps of 137 districts and counties in Shandong Province of China from 2018 to 2022 by combining time series spectral features and textural features derived from Sentinel-1 and Sentinel-2 images provided by GEE cloud platform. Afterwards, we designed a GPC-based urban development vigor index (GPC-UDVI) to evaluate the vitality of each city, which offers a novel perspective to identify shrinking cities. Experimental results demonstrated that the average overall accuracy of GPC maps is 89.696 %, which is accurate enough for the following analysis. Besides, the proposed GPC-UDVI exhibits a consistent trend with statistical data and could reveal urban development patterns with a high performance. Above all, dynamic monitoring of urban GPC through remote sensing is significant for understanding urban expansion modes and aiding in urban reconstruction management.

A Grassroots Alternative to Urban Shrinkage? A Comparative Analysis of Place Reputational Remaking in Buffalo and Cleveland

This article explores how local actors in Buffalo and Cleveland mobilized through garden tourism as a form of alternative urbanism to rehabilitate heavily stigmatized places and remake their city's reputations. Buidling off the concepts of civic action and scene styles, I compare how grassroots actors in Buffalo mobilized through a symbolic purity scene style to deracialize urban stigmas to how grassroots actors in Cleveland mobilized through a diversity scene style to create an inclusive place reputation that addressed the city's internal racial and ethnic divsions. I found that in the process of rehabbing their communities, grassroots actors in both cities replaced racialized urban stigmas with a different form of Whiteness, and when residents and elites shared the same scene style, they were more likely to cooperate, which entrenched the garden tour with local elites and other organizations in the cultural tourism field. Cultural variables like a place's reputation matter in how and what kind of Rust Belt city will emerge from the era of urban shrinkage. Data for this article comes from 50 semistructured in-depth interviews, fieldwork, and archival data.

Can Acceptance of Urban Shrinkage Shift Planning Strategies of Shrinking Cities From Growth to De-Growth?

Shrinking cities scholars claim that planning actors in the cities where shrinking is accepted are more likely to change the focus of planning strategy from pursuing growth to actively planning for de-growth. Considering this argument, this article investigates to what extent planning actors in shrinking cities seek solutions outside the dominant growth paradigm if they accept the reality of shrinkage. This is accomplished by examining the comprehensive plans of 18 shrinking cities in the Rust Belt area of the US and establishing relations between the interpretations of urban decline expressed in these planning documents and the resulting planning visions and strategies. The findings demonstrate that although planning actors in most analysed cases accepted urban shrinkage as a reality and adopted a vision of a smaller future city, they mainly devised strategies that facilitate growth. This suggests that urban planning may be far less impacted by specific interpretations of shrinkage, including acceptance, than what is popularly believed to be the case. Instead, growth remains a focal point of most planning efforts in shrinking cities, even when planning actors acknowledge it may not be realistically attainable.