Esmond Birnie: There is no evidence of a significant difference in the Covid-19 death rates between north and south

Like most comparisons of statistics across frontiers this is not easy to do.

Subject to caveats, the most recent official statistics suggest that whilst the cumulative death rate in NI may be higher than that in the RoI this is not by a very large margin (about 15%).

NI’s apparently higher rate might be a result of the probably wider definition used — any case where Covid is mentioned on the death certificate and not just those with a positive test for Covid-19 — as compared to the definition in the RoI: tested positive plus the “probable and suspected”.

Death rates in both NI and the RoI appear to be well below those in Great Britain.

Even if one accepts the NI death rate is higher than that in the RoI, notwithstanding some previous commentators, this need not imply that gap can be attributed to the different public policy response in the two jurisdictions.

In terms of vulnerability to Covid-19 NI’s population has two major characteristics pre-disposing it towards a higher death rate: population density is about twice as high and the share of 65+s is also higher.

These two structural characteristics could explain much of the gap in death rates.

On May 20 Professor Mike Tomlinson published the article ‘Why is it so hard to compare statistics on island of Ireland’ in The Irish News.

He claimed it was likely NI’s death rate was very much higher than that in the RoI — by perhaps 50% (similarly, his article in the Irish Times, April 22). Other commentators have disagreed with his conclusion: See a recent Policy Exchange Report (Professor Graham Gudgin May 6, Covid-19 across Ireland).

This exercise is not as straightforward as might be hoped — there are uncertainties about how far the data include all deaths related to Covid, it is unclear how like is really being compared to like, and there are lags in terms of how up-to-date the results are.

Here is a comparison based on the most up-to-date data for NI:

These figures, obviously already more than a week out-of-date, indicate a death rate NI which is about 12% higher than that in the RoI — a difference but not a substantial one.

By comparison, in his two articles, Professor Tomlinson suggested the rate in NI could be “between 41% and 50% per above” (Irish News, May 20) or “up to 50% higher than the Republic’s” (Irish Times, April 22) but some of his comparisons are based on a different measure “excess deaths or mortality” — in other words, how far were deaths in each week since early March higher than “normal” figures.

That difference is attributed to Covid (people who die directly because of Covid or because of the wider consequences of the virus especially in terms of reduced access to wider healthcare).

NISRA data allow an excess death figure to be measured for NI. In the case of RoI one has to rely on a source other than official statistics — the online database of death notices (RIP.ie) as used by the University College Dublin economist Seamus Coffey.

Such calculations are subject to several caveats.

First, a baseline has to be identified so we can say what was the “normal” number of deaths but is the baseline convincing?

Second, how valid is the assumption that 100% of the excess deaths can be attributed to Covid? [Note 1].

How much stress should be placed on the difference between the NI and RoI rates?

Is it an indicator of some sort of policy failure in NI [Note 2]. I doubt if it is as straightforward as that.

This is because there are other plausible explanations for the difference in death rates between NI and the RoI.

NI has a much higher population density (high density makes rapid spread of the virus more likely because social distancing is harder) and also a higher elderly population (over 60s are generally much more liable to die from Covid).

At the same time, given a higher proportion of the population from black and minority ethnic backgrounds, the RoI’s susceptibility to Covid-19 deaths may have been somewhat increased (though given that the population share difference is only about three percentage points probably not by enough to outweigh the favourable impact of having a younger and less dense population) [Note 3].

These three factors are considered in turn:

1. NI’s much higher population density

In 2018 136 persons per square kilometre. About twice that of the RoI: 71.

A diagram [accompanying Dr Birnie’s paper on NI-RoI differences] shows that across Europe higher population density is generally associated with relatively higher COVID-19 death rates. Only European countries are used since these will be at a broadly similar point in the development of the virus.

Of the “countries” shown, NI ranks 9th out of 22 in terms of population density (see Annex for the underlying data). High population density countries such as the Netherlands, Belgium and the UK have some of the highest COVID-19 death rates. Admittedly, some lower density countries such as France, Spain and Sweden also have relatively high death rates. Interestingly, this data suggests that rather than the RoI’s death rate being relatively low but it looks out of line compared to other European countries with very low population densities.

2. NI’s older population

In 2011 (the last population census in both jurisdictions) 14.7% of NI’s population was aged 65 or more compared to 11.7% in RoI.

3. NI’s lower Black and minority ethnic (BAME)

In 2011 the percentage share of non-white ethnic was 1.7% in NI but 5.8% in the RoI.

A final point regarding such comparisons- we can be reasonably confident that the COVID-19 death rate in NI and the RoI has been substantially lower than that in GB (60-70% of the UK average). However, it would probably be complacent to claim that this is because policy has been better in NI or the RoI.

Once again, there is the important fact that population densities in both NI and the RoI are much lower than in England. Also, NI and the RoI are probably several weeks behind England in terms of the development of the virus.

• Esmond Birnie is senior economist, Ulster University Business School

1. Irish academics Dr. G. McCarthy and Dr. P. MacCarron provide a useful summary of the RIP.ie data in their Brainstorm blog for RTE 7 May 2020

https://www.rte.ie/brainstorm/2020/0505/1136496-death-notices-ireland-coronavirus/

Use of such data to indicate COVID-19 mortality may not be straightforward. Irish death notices were already well above the 10 year average in February 2020 before any major impact of the virus. Notices throughout 2019 were also above the 10 year average.

2. Here is Professor Tomlinson’s rationale: “The purpose of the original Irish Times article was take two jurisdictions that had adopted very different policies in terms of lockdown and particularly in terms of testing strategies. I asked the simple question: Has this resulted in a different outcome in terms of deaths? It appeared to me that there was very strong evidence that it had” (Irish News, 20 May 2020).

3. It is now well established that the BAME population in the UK has had a much higher COVID death rate than the population average although the reasons for this are still disputed and subject to further research. The BAME population COVID- 19 death rate may similarly be relatively high in NI and the RoI.

• Sources: For COVID-19 death rates 22 or 20 May: NISRA, Wordometer (The Times, 23 and 21 May 2020). For population densities World Bank (2020) and for NI Statista.com.

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