||(0.00596)|(0)|(0.403)|(0)|
|---|---|---|---|---|
|Observations|8,352|8,381|145|145|
|Number of settlements|288|289|5|5|
|District Fixed effect|Yes|Yes|Yes|Yes|
|Time Fixed effects|Yes|Yes|Yes|Yes|

Standard errors in parentheses *** p<0.01, ** p<0.05, * p<0.1

# Appendix D. Robustness tests

## Variation in settlements’ buffer sizes

Robustness checks will be run, by modifying the monthly NTL values associated to each settlement, through changes in the size of the catchment area around settlements GPS points (from 1km to 2 and 5km radius). As discussed earlier, we do not have information on the actual settlements’ borders, and must rely on averaging NTL values around the given GPS location. While the study focused on a 1km-by-1km cell, this section extracts the average NTL values observed within 2 and 5km radius around the IOM settlements GPS point. As a reference, a 2km distance would take roughly a 20min walk, while 5km would be completed in 1hour. Summary statistics are available in Table 5.0.1.

_Table 5.0.1. Summary statistics of NTL levels, average across 2km and 5km radius around GPS points_

|Variable<br>Observations|Mean|Std. Dev.|Min|Max|
|---|---|---|---|---|
|NTL(average across 2km radius)<br>9,702|0.31|0.11|0.04|1.63|
|NTL(average across 5km radius)<br>9,702|0.31|0.14|0.03|1.85|
|_Source: Authors’ comp_|_utation_||||

Linear results are robust to the construction of NTL average based on a 2km and 5km radius instead of 1km, and the 5km radius results suggest an even stronger positive correlation between Net Inflow and NTL growth. The 2km radius analysis suggests that a marginal increase in _Net Inflow_ would increase the NTL levels in settlements which had a past NTL levels larger than 0.64. The 5km radius analysis shows that a marginal rise in _Net Inflow_ would always be associated with an increase in NTL levels.

Quadratic results become more complex when using the NTL average based on a 2 and 5km radius instead of 1km, as some results differ.

In inbound areas:

- Using the 2km radius, a marginal increase in Net Inflow would increase NTL level when the initial level of human activity is low enough (for NTL below 0.22), while the 5km radius analysis suggest that this is true (for NTL below 0.31), provided that the settlement is an important receiver of net inflows, i.e., the Net Inflow is high enough.

- Using the 2km radius average for NTL values, equation (7) can be decomposed as d NTLi,t ≡ h( N ) + Xi .f( N ), since d NTLi,t = −3.44e<sup>−06</sup> + 1.97e<sup>−05</sup> N dXXii − 2.37eLL<sup>−05</sup> ii,tt−1N 2 + 2. Xi LLii,tt−1 −5.95e<sup>−11</sup> N dXXii + 7.66e<sup>−11</sup> N 2 ) . One finds that LLii,tt−1 f(NTL) is positive whenever NTL < 0.22 or whenever NTL >0.56. The function h(NTL) is positive when ii,tt−1 ii,tt−1 ii,tt−1

- LL (9.40NN<sup>−12</sup> LL LL

- NTL in [0.25; 0.79].

- `o` Using the 5km radius average for NTL values, equation (7) can be decomposed as d NTLi,t = 2

- −5.1e<sup>−06</sup> + 1.87e<sup>−05</sup> N − 5.75e<sup>−05</sup> N + 2. Xi −6.05e<sup>−11</sup> N dXXii) ≡ h(NTL) + Xi .f( N ), with I One finds that f( N )>0 whenever N < ii,tt−1 ii,tt−1 ii,tt−1

- LL LL (1.88NN<sup>−11</sup> LL

- ii,tt−1 ii,tt−1 ii,tt−1

- LL = NNPPNNTTII I PPww. LL LL