Japan police tackle prostitution in Osaka nightlife area with Nobel-winning 'nudge theory'

The Mainichi

11-05-2025

OSAKA -- In the bustling nightlife district near Osaka's Umeda area is a narrow street known for attracting women engaged in prostitution and men seeking their services. Locals whisper warnings such as, "Never go there," cautioning their children against setting foot in the notorious lane.
Recently, residents and police have teamed up to transform the environment of this troubled street. Drawing inspiration from a Nobel Prize-winning economist's concept, their efforts are yielding promising results, complemented by measures encouraging women to reconsider getting into prostitution.
Just off the vibrant main streets bustling with young locals and foreign tourists, near the Toganocho district of Osaka's Kita Ward, lies a municipal road roughly 100 meters long, surrounded by hotels and commercial buildings. Its secluded nature made it ideal for illicit rendezvous, and there were visitors constantly. Some neighborhood families strictly instructed their children to avoid the area entirely.
Street gains notoriety through social media as prostitution hotspot
According to Osaka Prefectural Police, women believed to be engaging in prostitution started appearing on this street around 2022, and social media posts led to its widespread recognition as a "prostitution hotspot."
Police arrested or referred to prosecutors 30 people for prostitution-related offenses (soliciting customers) during a little over a year through late November 2024. Sonezaki Police Station, which oversees the street, enhanced patrol frequency and collaborated with locals to put up posters with messages such as, "Waiting to solicit customers is illegal," but their actions yielded few tangible results.
Starting last summer, the prefectural police began talks with Osaka Municipal Government officials and locals, incorporating expert advice to come up with more effective strategies.
Decision to apply Nobel laureate's 'nudge theory'
Their chosen approach was based upon "nudge theory," a concept from behavioral economics proposed by Nobel Prize-winning American economist Richard Thaler. "Nudge" refers to lightly prompting or gently influencing someone's behavior toward making better choices. Nudge theory aims to shape people's decisions subtly -- without forced compliance -- through analyzing and influencing behavioral motivations.
Takahito Shimada, a professor at Shiga University and former head of the crime prevention research division of the National Police Agency (NPA)-affiliated National Research Institute of Police Science, collaborated on the initiative. According to Shimada, narrow spaces surrounded by tall structures often do not cause stress even when people stay there for extended periods. He explained, "This problematic street acts like a hidden spot. The secluded layout enables women to solicit clients without fear of being observed."
Painting the street yellow to deter solicitation
Considering Shimada's analysis, authorities painted the street surface yellow, a color typically associated with caution or warnings. The goal was to subconsciously alert visitors and discourage them from lingering.
Additionally, authorities commissioned art students from a nearby vocational school to create a series of 10 illustrations depicting fish swimming toward the street's exits. Installed along the pavement, these aquarium-themed images were intended to further motivate pedestrians to move through quickly. Locals warmly welcomed this creative touch.
Road painting and artwork placement concluded in December 2024. To evaluate the effectiveness of these interventions, plainclothes officers from Sonezaki Police Station conducted patrols four times daily for a week. The average number of people lingering per patrol dropped substantially, from 7.43 in November 2024 to just 0.86 in February 2025.
According to Shimada, using nudge theory to counter prostitution is unprecedented globally, making this initiative particularly groundbreaking.
Masafumi Fujino, 79, who leads neighborhood crime prevention efforts, praised the interventions, saying, "The street has become brighter, and people in our community are talking about how much easier it feels to pass through now." Police plan to continue patrols and monitor whether the positive changes endure.
However, some question if simply expelling women from one street may just push prostitution elsewhere. During public consultations, locals and police also voiced concern that officials should address factors forcing women into prostitution.
'Yellow cards' carry compassionate warnings to deter prostitution
To deepen their efforts, from March 2025, police prepared postcard-sized yellow cards for officers to distribute directly to women frequenting the problem street. While these cards feature explicitly written warnings that prostitution and solicitation are illegal -- hence "yellow card," symbolizing a caution -- they also include messages expressing care and support: "Your body and heart matter. There are people who genuinely want to protect you."
Officers from Sonezaki Police Station had personally witnessed women becoming victims of assault and robbery when accompanying clients into nearby hotels. Prompted by a desire to prevent similar abuse, officers created these cards with the heartfelt message: "We don't want you to feel afraid on these streets. Value yourself and stay safe."
Alongside the cards, police are handing out flyers produced by the city of Osaka that list contact details for accessible counseling services available through channels such as email and social media, hoping these resources provide support whenever women decide to seek alternative assistance and leave prostitution behind.
Ryo Kitagawa, who was head of Sonezaki Police Station's community safety division until the end of March, reflected, "Previously, there were cases where women we'd questioned simply returned to the street. While we remain vigilant in eliminating street prostitution, we also want the area to become a supportive environment for women facing difficult circumstances."