# Western Indonesia

The region comprising the other 21 provinces in Sumatra, Java, and Kalimantan is known as Western Indonesia.
Western Indonesia has a land border with East Malaysia to the North and Peninsular Malaysia to the West.

## History

Military action by the Dutch launched on 20 July 1947 against areas controlled by the Indonesian republicans, Operation Product, resulted in the Dutch regaining control of West and East Java, the areas around Medan, Palembang and Padang in Sumatra. The United Nations called for a ceasefire, and negotiations between the two sides led to the Renville Agreement of January 1948, with a ceasefire along the "Van Mook Line", which connected the most advanced Dutch positions. The Dutch then established states in the areas they had reoccupied, including East Sumatra (December 1947), Madura and West Java (February 1948), South Sumatra (September 1948) and East Java (November 1948). The leaders of these regions then established the Federal Consultative Assembly.
A second Dutch military action, Operation Kraai, aimed at destroying the Republic, was launched on 18 December 1948. Despite recapturing the major cities of Java, including the republican capital of Yogyakarta, and all of Sumatra except Aceh in the far north, it triggered the protest resignation of the cabinets of the State of East Indonesia and Pasundan (West Java) and the Sultan of Yogyakarta from his position as regional head.

## Geography
### Geology

The main islands of Sumatra, Java, Madura, and Kalimantan lie on the Sunda plate.
Indonesia has relatively high tectonic and volcanic activities. It lies on the convergence between the Eurasian, Indo-Australian, Pacific, and Philippine Sea plate. The Sunda megathrust is a 5,500 km long fault located off southern coasts of Sumatra, Java and Lesser Sunda Islands, where the Indo-Australian plate is thrusting northeastward towards the subducting Sunda plate. Tectonic movement in this fault is responsible for the creation of the Sunda Trench, and mountain ranges across Sumatra, Java. Mount Merapi, located in the Java portion of the megathrust, is the most active volcano in Indonesia and is designated as one of world's Decade Volcanoes due to the hazard it poses to the surrounding populated areas.

### Ecology

Borneo is the third largest island in the world and the native vegetation was mostly Borneo lowland rain forests although much of this has been cleared with wildlife retreating to the Borneo montane rain forests inland. Kalimantan and Sumatra, experience only slight differences in rainfall and temperature between the seasons, whereas others, such as Nusa Tenggara, experience far more pronounced differences with droughts in the dry season, and floods in the wet. Rainfall in Indonesia is plentiful, particularly in West Sumatra, Northwest Kalimantan, West Java.

## Administration

Western Indonesia is composed of three main geographic units: Kalimantan, Java and Sumatra.
| Code | Geographical unit | Provinces | Population (mid-2023) | Largest city | Highest point |
| ID-SM | Sumatra | Aceh, the Bangka Belitung Islands, Bengkulu, Jambi, Lampung, North Sumatra, Riau, the Riau Islands, South Sumatra, and West Sumatra | 60,756,400 | Medan | Mount Kerinci 3,805 m (12484 ft) |
| ID-JW | Java | Banten, Central Java, East Java, the Special Capital Region of Jakarta, the Special Region of Yogyakarta, and West Java | 155,645,500 | Jakarta | Mount Semeru 3,678 m (12067 ft) |
| ID-KA | Kalimantan | Central Kalimantan, East Kalimantan, North Kalimantan, South Kalimantan, and West Kalimantan | 17,259,000 | Samarinda | Mount Bukit Raya 2,278 m (7,474 ft) |

## Economy

Below are the top 13 provinces in Western Indonesia ranked by GDP in 2019:
| Rank | Province | Region | GDP (in billion Rp) | GDP nominal | GDP PPP |
| Rank | Province | Region | GDP (in billion Rp) | (in billion $) | (in billion $) |
| - | Indonesia | South East Asia | 16,073,257 | 1,136.72 | 3,329.17 |
| 1 | Jakarta | Java | 2,840,828 | 200.91 | 588.42 |
| 2 | East Java | Java | 2,352,425 | 166.37 | 487.27 |
| 3 | West Java | Java | 2,125,158 | 150.30 | 440.19 |
| 4 | Central Java | Java | 1,362,457 | 96.35 | 282.18 |
| 5 | North Sumatra | Sumatra | 801,733 | 56.70 | 166.06 |
| 6 | Riau | Sumatra | 765,198 | 54.12 | 158.51 |
| 7 | Banten | Java | 664,963 | 47.03 | 137.74 |
| 8 | East Kalimantan | Kalimantan | 653,677 | 46.23 | 135.40 |
| 9 | South Sumatra | Sumatra | 455,233 | 32.19 | 94.28 |
| 10 | Lampung | Sumatra | 360,664 | 25.51 | 74,71 |
| 11 | Riau Islands | Sumatra | 268,080 | 18.96 | 55.53 |
| 12 | West Sumatra | Sumatra | 246,423 | 17.42 | 51.01 |
| 13 | Jambi | Sumatra | 217,712 | 15.40 | 45.10 |
In 2012, the DMO was 24.72%. Starting from 2014, no low-grade coal exports are allowed, so the upgraded brown coal process that cranks up the calorie value of coal from 4,500 to 6,100 kcal/kg will be built in South Kalimantan and South Sumatra. Major Japanese factories are concentrated east of Jakarta with high concentrations in Bekasi, Cikarang and Karawang, West Java.

## Demographics
### Population

Jakarta is the largest city and the only megacity in Indonesia, with a population of 10.70 million. As a primate city, Jakarta is nearly four times larger than the second largest city Surabaya. Jakarta's status is unique compared to other cities in Indonesia, since it is technically a province with a city management. It is subdividied into five administrative cities and an administrative regency, which are not self-governed (without municipal council nor government budget). All five of Jakarta's satellite cities also have passed one million mark in population, with the largest one being Bekasi.
The other largest cities by region include Medan (Sumatra, also the largest outside of Java), Samarinda (Kalimantan).
Below are the populations of each provinces which make up the total population of Western Indonesia:
| Province | Population (2010 census) | Urban % in 2010 | Total Fertility Rate | Population (2015 census) |
| Aceh | 4,494,410 | 23.6 | 2.79 | 4,496,570 |
| North Sumatra | 12,982,204 | 42.4 | 3.01 | 13,923,262 |
| West Sumatra | 4,846,909 | 29.0 | 2.91 | 5,190,577 |
| Riau | 5,538,367 | 43.7 | 2.82 | 6,330,941 |
| Jambi | 3,092,265 | 28.3 | 2.51 | 3,397,164 |
| South Sumatra | 7,450,394 | 34.4 | 2.56 | 8,043,042 |
| Bengkulu | 1,715,518 | 29.4 | 2.51 | 1,872,136 |
| Lampung | 7,608,405 | 21.0 | 2.45 | 8,109,601 |
| Bangka Belitung Islands | 1,223,296 | 43.0 | 2.54 | 1,370,331 |
| Riau Islands | 1,679,163 | 67.4 | 2.38 | 1,968,313 |
| Banten | 10,632,166 | 52.2 | 2.35 | 11,934,373 |
| Jakarta | 9,607,787 | 100.0 | 1.82 | 10,154,134 |
| West Java | 43,053,732 | 50.3 | 2.43 | 46,668,214 |
| Central Java | 32,382,657 | 40.4 | 2.20 | 33,753,023 |
| Yogyakarta | 3,457,491 | 57.7 | 1.94 | 3,675,768 |
| East Java | 37,476,757 | 40.9 | 2.00 | 38,828,061 |

### Languages

Indonesia recognizes only a single national language, and indigenous languages are recognized at the regional level, although policies vary from one region to another. For example, in the Special Region of Yogyakarta, the Javanese language is the region's official language along with Indonesian. The next most widely spoken regional languages in the country are Sundanese, local Malay, and Minangkabau. There are hundreds of indigenous languages spoken in Indonesia. Most of them are locally used indigenous languages, a category of languages referring to those spoken at the local, regional level, spoken by a small number of people, ranging from a few to a few thousands of people. These include small languages such as Benggoi, Mombum and Towei. Other languages are spoken at the regional level to connect various ethnicities. For this reason, these languages are known as regional lingua francas (RLFs). According to Subhan Zein, there are at least 43 RLFs in Indonesia, categorized into two types: Malayic RLFs and Non-Malayic RLFs. The former refers to a group of regional lingua francas that are thought of as indigenised varieties of Malay or Indonesian. These include such languages like Banjar Malay among others. The latter refers to regional lingua francas that are not associated with Malay or Indonesian, like Iban.
The population numbers given below are of native speakers, excepting the figure for Indonesian, which counts its total speakers.
Largest languages in Indonesia :
| Language | Number (millions) | % of total population | Branch | Year surveyed | Main areas where spoken |
| Indonesian | 210 | 80.42 | Malayic | 2010 | Throughout Indonesia |
| Javanese | 84.3 | 32.28 | Javanese | 2000 (census) | Throughout Java Island and several provinces in Sumatra and Kalimantan islands. |
| Sundanese | 42.0 | 16.08 | Sundanese | 2016 | West Java, Banten, Jakarta |
| Madurese | 13.6 | 5.21 | Madurese | 2000 (census) | Madura Island (East Java) |
| Minangkabau | 5.5 | 2.11 | Malayic | 2007 | West Sumatra, Riau, Jambi, Bengkulu, Jakarta |
| Palembang Malay | 3.9 | 1.49 | Malayic | 2000 (census) | South Sumatra |
| Banjarese | 3.5 | 1.34 | Malayic | 2000 (census) | South Kalimantan, East Kalimantan, Central Kalimantan |
| Acehnese | 3.5 | 1.34 | Chamic | 2000 (census) | Aceh |
| Betawi | 2.7 | 1.03 | Malay-based creole | 1993 | Jakarta |
| Batak Toba | 2.0 | 0.77 | Northwest Sumatra–Barrier Islands | 1991 | North Sumatra, Riau, Riau Islands, Jakarta |
| Chinese-Min Nan | 1.3 | 0.50 | Sinitic (Min Nan) | 2000 | North Sumatra, Riau, Riau Islands, West Kalimantan |
| Batak Karo | 0.6 | 0.23 | Northwest Sumatra–Barrier Islands | 1991 | North Sumatra |
| Bangka Malay | 0.3 | 0.11 | Malayic | 2000 (census) | Bangka Island (Bangka Belitung) |
| Osing | 0.3 | 0.11 | Javanese | 2000 (census) | East Java |
| Gayo | 0.3 | 0.11 | Northwest Sumatra–Barrier Islands | 2000 (census) | Aceh |
| Chinese-Cantonese | 0.3 | 0.11 | Sinitic (Yue) | 2000 | North Sumatera, Riau Islands, Jakarta |

### Religion

Religion was a census variable in the 1961, 1971, 1980, 1990, 2000, and 2010 and in various intercensal surveys. Being deemed divisive, the 1961 census data regarding religion was not published. In 1971, three groups of Christians were recorded: Catholic, Protestant and other. The U.N. Demographic Yearbook 1979 only lists data collectively for all Christians. In the 2000 census, only Catholics and Protestants were available as categories.
Religious composition by ethnic group
| Ethnic Group | Muslims | Christians | Hindus | Buddhists | Confucians | Others | Total |
| Javanese | 92,107,046 | 2,428,121 | 160,090 | 90,465 | 2,857 | 9,599 | 94,788,943 |
| Sundanese | 36,450,022 | 29,332 | 1,851 | 24,528 | 4,854 | 155,308 | 36,665,892 |
| Malay | 8,643,370 | 8,484 | 1,031 | 19,848 | 1,243 | 242 | 8,751,218 |
| Batak | 3,738,660 | 4,707,658 | 1,476 | 9,190 | 315 | 6,305 | 8,463,604 |
| Madurese | 7,157,518 | 7,695 | 368 | 435 | 32 | 43 | 7,166,091 |
| Betawi | 6,607,019 | 151,429 | 1,161 | 39,278 | 1,805 | 252 | 6,800,943 |
| Minangkabau | 6,441,071 | 1,822 | 179 | 1,255 | 49 | 44 | 6,459,420 |
| Buginese | 6,348,200 | 35,516 | 26,102 | 957 | 47 | 2,395 | 6,413,217 |
| Bantenese | 4,634,374 | 4,810 | 101 | 2,680 | 70 | 242 | 4,642,277 |
| Banjarese | 4,108,104 | 15,775 | 994 | 1,396 | 62 | 410 | 4,126,741 |
| Balinese | 127,274 | 49,385 | 3,736,993 | 10,378 | 142 | 473 | 3,924,645 |
| Acehnese | 3,398,818 | 403 | 70 | 1,028 | 7 | 4 | 3,403,961 |
| Dayak | 1,016,697 | 2,017,870 | 12,140 | 17,502 | 568 | 154,219 | 3,218,996 |
| Sasak | 3,153,671 | 5,540 | 4,555 | 10,682 | 7 | 439 | 3,174,894 |
| Chinese | 131,682 | 1,211,692 | 3,552 | 1,388,829 | 94,005 | 1,114 | 2,830,874 |