An Equality Commission study for 2021 showed that 43.5% of the workforce was Protestant, 43.4%, was Catholic and 13.1% were "non-determined".
In 2001 the workforce composition was 59.7% Protestant and 40.3% Catholic.
The commission's chief said fair employment legislation laid down in 1991 was responsible for driving change.
"Northern Ireland's workforce composition as shown in this report is very different to what we saw 30 years ago," said Geraldine McGahey.
"The Fair Employment legislation was responsible for driving that change, and for proving that legal enforcement of rights could work."
Ms McGahey said the law had helped pave the way for the 1998 Good Friday Agreement that brought an end to the Troubles.
The Fair Employment and Treatment Northern Ireland Order bans discrimination on the grounds of religious belief or political opinion, so people cannot be "less favourably treated than others" because of their religion, presumed religion or political affiliation or because they do not hold any of these beliefs or opinions.
The latest statistics are based on a total monitored workforce of 564,296, of whom:
* 245,419 (43.5%) were Protestant
* 245,070 (43.4%) were Catholic
* 73,807 (13.1%) were non-determined (defined as "where a community background is neither stated nor can reasonably be determined")
* 52.4% were women
It also showed that for the 13th consecutive year, the Catholic community (52.8%) comprised a greater proportion of applicants than the Protestant community (47.2%).
In every year since 2006, members of the Catholic community (52.7%) comprised a greater proportion of appointees than did the Protestant community (47.3%).
The monitoring report noted that the overall picture for 2021 is subject to the circumstances of the Covid-19 pandemic.
There is an estimated under-reporting of approximately 1,700 employees.
The demographics of Northern Ireland have shifted slightly since the Good Friday Agreement.
In 2001 the census showed that 43.8% of the population had a Catholic background and 53.1% had a Protestant background.
The 2021 Census shows the proportion of theresident population with a Catholic background was 45.7% compared to 43.48% Protestant.
The number of people from a Catholic background and those listed as "non-determined" in the workforce has increased since the commission's last report for 2020 was published.
It showed 44.3% were Protestant, 43.9% were Catholic and 11.8% were non-determined.
Geraldine McGahey said that the changing dynamics of society in Northern Ireland meant reform of fair employment legislation was now needed.
"Any new legislation should build on the unique and highly successful fair employment provisions.
"It should be seen as a chance to strengthen and enhance the laws that have worked so well to make our workplaces less divided, more inclusive, and more accepting of difference," she said.
The 2021 report shows the breakdown of the monitored workforce in Northern Ireland by community background.
It uses data provided to the commission by private and public sector employers based on their workforces in 2021.