*2.4. Data Analysis*

Maps were prepared on the base of elementary data including annual rates of demographic increase by time window and prefecture, with the aim at identifying spatial similarities in population dynamics over shorter and longer time scales. A simplified framework was proposed with the aim at classifying prefectures on the base of long-term population trends. Criteria were oriented toward the identification of resilient territories under the assumption that prefectures attracting population over a sufficiently long time interval are considered demographically resilient and vice versa. Two criteria were adopted, considering 80 years (1940–2019) and two sub-periods of 40 years each (1940–1980; 1981–2019), representing, respectively compact-dense/radio-centric urbanization and decentralized suburbanization/counter-urbanization in Greece. Prefectures were classified as demographically resilient over the whole time interval (80 years) if the resident population increased for six, seven or eight decades; the reverse pattern characterized nonresilient districts with persistent population shrinkage. A similar framework was adopted over the two sub-periods, classifying prefectures as 'resilient' or 'nonresilient' if population, respectively grew (or declined) continuously for all the four decades in each sub-period. A pair-wise correlation analysis (based on Spearman nonparametric rank coefficients) was computed between each contextual variable (Section 2.3) and the annual rate of population variation (%) over (i) the whole study interval (1940–2019) or, separately, (ii) the two sub-periods (1940–1980 and 1981–2019). Significant correlations were delineated at *p* < 0.05 applying a Bonferroni's correction for multiple comparisons [69].

A hierarchical clustering (based on Euclidean similarity matrix under Ward's amalgamation approach) was run on a database constituted of population growth rates with the aim at classifying temporal units (years) and spatial units (prefectures). Assumed as a relevant dimension of demographic resilience, similar spatiotemporal structures characterize long-term population trends. Persistence (or change) in specific demographic trends was considered indicative of different background conditions. A principal component analysis (PCA) was carried out on a collection of variables including (i) population growth rates at eight decades, (ii) population density at the beginning of each decade and (iii) the remaining eight contextual variables (Section 2.3) at each prefecture. PCA was aimed at containing redundancy, evaluating changes over time in the multivariate relationship between variables at the same time. The PCA characterized research dimensions and distinctive demographic structures in Greece. components with eigenvalue > 1 were selected according to the results of the spectral decomposition of the correlation matrix [70]. The latent structure of variables and prefectures was finally illustrated adopting a biplot that depicts component loadings and scores. Multiple linear regression models were run for each decade and identified the predictors most associated with population growth in Greece. For each decade, predictors include the variables described in Section 2.3 and were standardized before analysis (e.g., [29]). Model's goodness-of-fit was estimated via adjusted R 2 tested for significance (against the null hypothesis of a statistically insignificant model) at *p* < 0.01 using a Fisher–Snedecor F statistic. Slope coefficient estimates and the related significance level at *p* < 0.1 were reported testing for the null-hypothesis of statistically insignificant coefficient based on a Student's *t* statistic.

### **3. Results 3. Results**

### *3.1. A Descriptive Analysis of Population Growth and Decline in Greece, 1940–2019 3.1. A Descriptive Analysis of Population Growth and Decline in Greece, 1940–2019*

hypothesis of statistically insignificant coefficient based on a Student's *t* statistic.

The resident population grew continuously in Greece between 1940 and 2001, declining slightly in the subsequent two decades (2001–2019). Figure 2 classified the investigated decades on the base of spatial diffusion (or concentration) of the population in Greek prefectures. A particularly rapid population increase in a few prefectures was observed during three decades (1951–1961, 1961–1971 and 1971–1981). Conversely, the population increase in the remaining five decades was slower and more dispersed over space. The largest diffusion of positive growth rates at the prefectural level was observed for the last two decades of investigation, corresponding with slightly negative growth rates at the national scale. The resident population grew continuously in Greece between 1940 and 2001, declining slightly in the subsequent two decades (2001–2019). Figure 2 classified the investigated decades on the base of spatial diffusion (or concentration) of the population in Greek prefectures. A particularly rapid population increase in a few prefectures was observed during three decades (1951–1961, 1961–1971 and 1971–1981). Conversely, the population increase in the remaining five decades was slower and more dispersed over space. The largest diffusion of positive growth rates at the prefectural level was observed for the last two decades of investigation, corresponding with slightly negative growth rates at the national scale.

*Sustainability* **2020**, *12*, x FOR PEER REVIEW 6 of 19

hypothesis of a statistically insignificant model) at *p* < 0.01 using a Fisher–Snedecor F statistic. Slope

**Figure 2.** Relationship between the percent annual rate of population growth (%) in Greece and the relative proportion of prefectures with positive growth rates. **Figure 2.** Relationship between the percent annual rate of population growth (%) in Greece and the relative proportion of prefectures with positive growth rates.

By partitioning the investigated period in two-time windows, Figure 3 illustrates a substantial similarity in the geography of population expansion in Greece. Positive rates were observed in prefectures along the Aegean side from Macedonia to Crete, being more intense during 1940–1980 and less intense during 1981–2019. Marginal prefectures in Central Greece and Peloponnese have totalized the highest decrease in the country. A total of 18 prefectures (including Attica and Thessaloniki) were classified in the lowest right quadrant of Figure 3, indicating higher growth rates during 1940–1980 than during 1981–2019. By partitioning the investigated period in two-time windows, Figure 3 illustrates a substantial similarity in the geography of population expansion in Greece. Positive rates were observed in prefectures along the Aegean side from Macedonia to Crete, being more intense during 1940–1980 and less intense during 1981–2019. Marginal prefectures in Central Greece and Peloponnese have totalized the highest decrease in the country. A total of 18 prefectures (including Attica and Thessaloniki) were classified in the lowest right quadrant of Figure 3, indicating higher growth rates during 1940–1980 than during 1981–2019.

These prefectures include urban, high-density areas (Athens, Thessaloniki, Iraklio, Patras, Larisa, Viotia, Argolida) expanding mostly with compact urbanization (1940–1960). A total of 33 prefectures were classified in the highest left quadrant of Figure 3, indicating higher growth rates during 1981–2019 than during 1940–1980. These prefectures include rural, coastal districts and islands with low and moderate density settlements, expanding mostly in the subsequent suburbanization phase (Figure 4).

Spatial persistence in growth rates was illustrated in Figure 5 considering together the whole study period and two separate time intervals. Prefectures with continuous population growth over six, seven or eight decades concentrated along the Aegean side from Macedonia to Crete. These prefectures (*n* = 13 out of 51) host cities constituting the highest rank of the Greek metropolitan hierarchy. Prefectures with continuous population decline (*n* = 4) were located in Central-Western Greece and Peloponnese. Between 1940 and 1980, continuously positive population growth rates at the decadal scale were observed in six prefectures that include urban areas around Athens and Thessaloniki, as well as in Crete (Iraklio), reflecting the tumultuous expansion of the three largest cities in Greece. Continuously negative rates of population increase were observed in Central Greece, Peloponnese and Northern Aegean region (*n* = 7). Between 1981 and 2019, continuously positive rates of population expansion were recorded only in the Cyclades and Eastern Macedonia (*n* = 2 prefectures). Continuously negative population growth rates were recorded in one prefecture of Western Greece. *Sustainability* **2020**, *12*, x FOR PEER REVIEW 7 of 19

*Sustainability* **2020**, *12*, x FOR PEER REVIEW 7 of 19

**Figure 3.** Relationship between the annual population growth rate (%) over two-time intervals in the recent history of Greece. **Figure 3.** Relationship between the annual population growth rate (%) over two-time intervals in the recent history of Greece. phase (Figure 4).

**Figure 4.** Spatial distribution of annual population growth rates (%) in Greek prefectures over 1940– 1980 **(a)** and 1981–2019 **(b)**. **Figure 4.** Spatial distribution of annual population growth rates (%) in Greek prefectures over 1940–1980 (**a**) and 1981–2019 (**b**).

**(a) (b)**

Spatial persistence in growth rates was illustrated in Figure 5 considering together the whole study period and two separate time intervals. Prefectures with continuous population growth over six, seven or eight decades concentrated along the Aegean side from Macedonia to Crete. These prefectures (*n* = 13 out of 51) host cities constituting the highest rank of the Greek metropolitan

**Figure 4.** Spatial distribution of annual population growth rates (%) in Greek prefectures over 1940–

1980 **(a)** and 1981–2019 **(b)**.

Spatial persistence in growth rates was illustrated in Figure 5 considering together the whole

hierarchy. Prefectures with continuous population decline (*n* = 4) were located in Central-Western Greece and Peloponnese. Between 1940 and 1980, continuously positive population growth rates at the decadal scale were observed in six prefectures that include urban areas around Athens and Thessaloniki, as well as in Crete (Iraklio), reflecting the tumultuous expansion of the three largest cities in Greece. Continuously negative rates of population increase were observed in Central Greece, Peloponnese and Northern Aegean region (*n* = 7). Between 1981 and 2019, continuously positive rates of population expansion were recorded only in the Cyclades and Eastern Macedonia (*n* = 2 prefectures). Continuously negative population growth rates were recorded in one prefecture of

**Figure 5.** Temporal persistence of population growth rates in Greek prefectures **(a)** prefectures with at least six decades with positive (or negative) growth rates over 1940–2019; **(b)** prefectures with four decades with positive (or negative) growth rates over 1940–1980; **(c)** prefectures with four decades **Figure 5.** Temporal persistence of population growth rates in Greek prefectures (**a**) prefectures with at least six decades with positive (or negative) growth rates over 1940–2019; (**b**) prefectures with four decades with positive (or negative) growth rates over 1940–1980; (**c**) prefectures with four decades with positive (or negative) growth rates over 1981–2019).
