Last week it was announced that $500,000 rewards were now on offer for information leading to convictions in multiple unsolved Tasmanian deaths including those of North-West residents Helen Munnings and Simon Crisp.

A police spokesperson said information had been provided following the increase of rewards in recent years, but did not say whether such information had ever led to a conviction.

Similarly, no answer was provided to a question about whether there was academic study or scholarly evidence which Tasmania Police based increasing the rewards this time.

Instead, Crime and Intelligence Commander Ian Whish-Wilson said it was done in other places and police "believe" it worked.

"Tasmania Police and Crime Stoppers have received several pieces of information in relation to the cases where rewards were increased," he said.

"This information will be assessed by relevant investigative areas."

Ms Munnings disappeared in 2008 and her body has never been found, and Mr Crisp was fatally shot at the Marrawah Tavern in 2013.

No one has been charged for either of their deaths, though both cases continue to loom large in the public conscience.

Two years ago today, Tasmania Police increased the reward for information leading to a conviction in Ms Munnings' death from $50,000 to $250,000.

At the time, Western District Commander Debbie Williams said the reward "may well serve as the driving factor" to motivate somebody with information to come forward.

"Investigators have long held the view that there are people in the community who have knowledge of Helen's disappearance who, for whatever reason, have not either been able to come forward or have been unwilling," she said.

Similarly, Commander Whish-Wilson on Wednesday said the rewards had been increased because people's circumstances may have changed.

"Rewards are commonly used in police jurisdictions around the world to entice people with information about unsolved crimes to come forward," he said.

"In the passage of time someone's circumstances and allegiances may have changed and the offer of a life-changing amount of money may be the motivation they need to come forward.

"We want the people who know about these cases to really re-consider their circumstances and allegiances and come forward with information.

"We believe $500,000 could offer someone the chance of a fresh start."