||**No.**<br>|**No. me**|**tro districts**|<br>**P**|**opulatio**|**n**|**Land**|<br>**area**|**Largest Metro**|
|---|---|---|---|---|---|---|---|---|---|
||**Metros**|||||||||
|**Threshold**|<br>**(Java-Bali)**|<br>**total**|**avg per**<br>**Metro**|**Total**<br>**(mil.)**|**% IDN**|<br>**Urban**|**Total**<br>**(km**<sup>**2**</sup>**)**|**% IDN**|**Name**<br>**(no. districts)**|
|UC|18(8)|135|7.5|144.24|57.2|88.37|145,260|7.7|Central-East Java(55)|
||||**THRES**<br>|**HOLDI**<br>|**NG OF N**<br>|**TL DAT**<br>|**A**<br>|||
|5th pct|8 (3)|118|14.8|130.89|51.9|86.00|109,702|5.8|Java (91)|
|10th pct|9 (4)|114|12.7|129.12|51.2|85.46|105,065|5.6|West-Central Java (33)|
|25th pct|9 (4)|109|12.1|125.66|49.9|83.76|97,858|5.2|West-Central Java (33)|
|30th pct|9 (4)|105|11.7|122.39|48.6|82.84|93,750|5.0|West-Central Java (33)|
|40th pct|9 (5)|89|9.9|111.68|44.3|78.79|78,113|4.1|West-Central Java (31)|
|50th pct|9 (6)|83|9.2|107.16|42.5|77.49|69,036|3.6|West-Central Java (31)|
|60th pct|9 (6)|69|7.7|92.05|36.5|71.72|50,125|2.6|Northwest Java (26)|
|70th pct|10 (7)|52|5.2|76.42|30.3|63.20|35,424|1.9|Jakarta-Bandung (22)|
|80th pct|8 (7)|41|5.1|64.42|25.6|55.39|25,382|1.3|Jakarta (15)|
|90th pct|5 (4)|21|4.2|38.16|15.1|36.24|8,110|0.4|Jakarta (11)|
|95thpct|3(3)|13|4.3|26.18|10.4|25.99|2,633|0.1|Jakarta(9)|

**_Notes:_** (Urban) Population data based on the 2014 Indonesian household survey (Survei Sosial Ekonomi, SUSENAS).

# **_Duranton Algorithm_**

As expected, the number of metro areas, the total number of districts that compose those metro areas, the total (urban) population living in metros, as well as the total land area covered by them, all steadily increase as the commuting flow threshold is lowered from 27 percent to 7 percent. At a threshold of 27 percent, we find a single metro area (Bandung) comprised of two districts that has an entirely urban population of just over 3 million and an area of 191 km<sup>2</sup> . A second metro area (Jakarta Selatan), also comprising two districts, then appears at a threshold of 23 percent, more than doubling the overall urban population that lives in metro areas to 6.7 million and the total land area covered by metro areas to 513 km<sup>2</sup> . By the time the threshold reaches 10 percent, which is Duranton’s preferred threshold in his application to Colombia, the number of metro areas has increased to 24, 17 of which are located on Java – Bali. The aggregate population of these metro areas is 64.5 million (25.6 percent of Indonesia’s population) with an urban population of 51.1 million. Together, the metro areas cover just over 54,000 km<sup>2</sup> or 2.2 percent of Indonesia’s total land area. At the lowest threshold of 7 percent, the number of metro areas has reached 39, 18 of which are on Java – Bali, with an aggregate population of 97 million and an overall urban population of 72.7 million. These metro areas collectively cover 110,197 km<sup>2</sup> .

Interestingly, regardless of the threshold used, the average number of districts per metro area remains small, increasing steadily from two at a threshold of 27 percent to 2.8 at a threshold of 9 percent before subsequently declining to 2.6 at a threshold of 7 percent. This turns out to be a defining feature of this approach: reducing the commuting threshold mainly has the effect of increasing the number of metro areas rather than the spatial extent of those metro areas. Finally, it is also notable that only as the threshold is lowered below 10 percent, more and more metros start appearing outside of Java – Bali. Using the 10% threshold identifies 24 metro areas of which 17 are on Java-Bali. Reducing the threshold further from 10 to 7 percent adds 15 additional metro areas, of which only 1 is on Java – Bali (see also Figure A2 in Appendix A). Also, it is not until a 10