KOTA KINABALU • In 1970, Sabah's population of 636,431 accounted for 6.1 per cent of Malaysia's 10.4 million.
By 2010, the proportion had nearly doubled to 11.3 per cent, with the state's population nearly quintupling in that time to 3.1 million.
In four decades, the nation's population grew by just 165 per cent and the increment in neighbouring Sarawak was just 148 per cent.
For critics of the Umno-led Barisan Nasional (BN), the maths implies that more than half the people in Sabah are migrants without permission (PTI), given that many Sabahans have moved to the peninsula and even Singapore for work.
Undocumented migrants have crossed the porous eastern seaboard from the Philippines for decades, especially since the archipelago's 1972 civil war. Many business owners, especially in plantations, used them as cheap labour.
Many acquired fake or illicit documents to masquerade as refugees, or even citizens, although it is impossible to ascertain the scale. Nonetheless, close to 600,000 have been deported since 1990.
But the most controversial dimension of the PTI issue is the naturalisation of foreigners to skew the electoral roll that allegedly began in the 1970s.
This accelerated after Umno's entry into Sabah in 1990, and political pressure led to a Royal Commission of Inquiry on Sabah's illegal immigrants in 2012, largely focusing on the so-called Project IC.
Former politician Chong Eng Leong, one of the most prominent voices on the migrant issue, has claimed that over 700,000 citizenships were handed out under the scheme in the 1990s, with about a third of them registered as voters.
"This Project IC is Project Mahathir. These voters were fixed deposits (for Umno)," he told The Sunday Times, referring to Tun Dr Mahathir Mohamad, who was premier from 1981 to 2003 when the scheme was introduced.
Since BN was toppled in 2018, Sabah's new Chief Minister Shafie Apdal has been accused of wanting to open the door to Filipino Suluks.
They are a Muslim ethnic group that is concentrated in both the southern Philippines and east Sabah, where the Parti Warisan Sabah president is from.