MLA: I'm astonished by lack of convictions
Police statistics obtained by this newspaper reveal that between April 2011 and July this year, officers recorded 5,092 deliberate blazes. A total of 565 people were arrested - but charges were only brought in 210 cases.
Put simply, it means the vast majority of arsonists are not facing justice.
The cases still unsolved include the deaths of a mother and daughter in Dungannon in April 2012. Betty and Deirdre McGirr died when an inferno started deliberately swept through a block of flats at Dunlea Vale in the town. Despite a high-profile PSNI investigation, no one has been arrested in connection with the blaze.
In the 12 months to April this year, the PSNI recorded 1,496 arson attacks. In the same period just 165 people were arrested and 65 charged.
Between April and July this year, another 513 arson incidents were recorded, with only 41 arrests and 17 people charged.
The figures for arrests and charges may not always correspond to the number of incidents in each year, since someone may be detained over an arson offence in a previous year. However, the general pattern since 2011 shows that only a small number of arson attacks results in someone facing criminal charges.
Ulster Unionist MLA Tom Elliott, who sits on the Assembly's justice committee, said: "The figures are quite astonishing. You can never expect to have every crime solved, but this figure is extremely low. I do think that the PSNI needs to improve on these figures as a matter of priority."
However, SDLP MLA Alban Maginness said there may be reasons for the low number of people brought to justice.
"Arson is a crime which can be difficult to detect," he said. "A lot depends on forensic evidence, and whether enough evidence survives to detect those responsible."
PSNI Assistant Chief Constable Stephen Martin said: "Arson can be a very serious offence, especially where there is a risk of substantial damage to property, or where life is endangered. In such circumstances, these incidents are subject to a full and rigorous investigation.
"We would of course like to see the outcome rates for these offences improve. Policing is always more successful when working in partnership with the community. To that end we would encourage anyone to report incidents of this nature promptly and to assist us if they have any information."