Japanese paper manufacturers were expecting a shrinking market due to the declining population but are expanding output instead due to an unexpected boost -- a surge in foreign tourists pushing up demand, inevitably, for toilet paper.

An industry official said the current situation was unforeseeable "10 years ago, when we thought the market would shrink due to the aging population and low birthrates."

(Supplied photo)

However, Nippon Paper Industries Co., Daio Paper Corp., Oji Holdings Corp. and Mitsubishi Paper Mills Ltd. have all moved to produce more paper beginning this year or next year, on the heels of a record 28.69 million foreigners visiting Japan in 2017.

According to estimates by the governmental Japan Tourism Agency, foreign tourists spent 4.42 trillion yen ($40 billion), an all-time high, in Japan that year, with industries including hotels, public transportation, home electronics and cosmetics notably benefiting.

But the toilet paper business is also gaining financially from the surge in visitors, as demand for the rolls has grown from hotels.

Government statistics show domestic sales of toilet paper has been moving in sync with the number of foreign visitors to Japan over the past several years.

The number of foreign visitors has grown for six consecutive years since 2012, the year after a magnitude 9.0 earthquake devastated northeastern Japan, triggering tsunamis and meltdowns at the Fukushima Daiichi nuclear power plant.

The value of toilet paper sales has increased for four consecutive years since 2014.

According to the Japan Paper Association, an industry body, demand for paper for printing use has been decreasing. But that for toilet paper and tissue paper is expected to continue growing.

The government aims to further boost the number of tourists to 40 million in 2020, when Tokyo hosts the Olympic and Paralympic games, and 60 million in 2030.