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What we would like to know – but have not yet found an answer for

At Our World in Data we bring together research and empirical data so that we can see how the world is changing. We do this across a very broad range of topics — from poverty to population growth, global health to international trade, energy production to agricultural yields — by drawing on international datasets, peer-reviewed research and empirical analyses.

Still, there are some burning questions that we would like to know, but have not yet found the answer to. Or in some cases, would require significant research projects to answer.

Below we list some of the outstanding questions we are keen to understand better. If you can help us answer them: whether through existing research publications that we are not aware of, trusty datasets, insights we may have missed, or are interested in working on such a project then please do get in touch. You can email us at: hannah@ourworldindata.org. Any additional inputs would be greatly appreciated (by both the team and those that use our content).

This page is regularly updated with new questions we have (or have answered) as they emerge.

What We Would Like to Know

What did population dynamics (or the population pyramid) look like pre-1950?

Currently we have very long-term global population estimates (dating back to 10,000 BC), with national estimates (derived from Gapminder and the United Nations) over the last few centuries. However, estimates of this breakdown in terms of the number of deaths and births in any given year typically only dates back to the year 1950. The earliest population pyramid therefore exists for the year 1950.

We would like long-term demographic trends that would allow for the construction of even earlier population pyramids, derived through longer-term (pre-1950) estimates on birth and death rates by age.

How and to what extent have controlled family planning methods been used to date?

Family planning is a key factor explaining fertility rates. In an article published in Science in 1994, John Bongaarts wrote: “By 1990 most governments of developing countries had adopted policies to reduce population growth, and 85% of the Third World’s population now lives in countries in which the government considers the fertility rate too high. Most of these countries have implemented family planning programs, but the efforts and resources devoted to them vary widely, and the coverage and quality of services in many family planning programs need to be greatly improved.”

How has this changed over time? How and to what extent have controlled family planning methods and policies, including coercive measures, been used to date?


How has global biodiversity changed over the long-term?

Biodiversity is a complex topic to gather data on — so many known (and still unknown) species across a span of biological levels makes this hard to monitor. This is especially true when trying to derive trends through time.

We are interested to better understand large-scale global or regional changes in biodiversity over the long-term. Location or species-specific studies are undoubtedly useful, but make it challenging to interpret whether these are discrete examples or are reflected in overall global change. The largest-scale estimates on biodiversity change we are aware of is the Living Planet Index. We are very interested to find more/better or longer-term sources on these trends.

How has soil fertility changed over the long-term?

Our content under ‘Food’ documents the long-term changes across many agricultural components, including production, yields, land use, inputs. We have also covered large meta-studies on the relative environmental impacts of Organic vs. Conventional Agriculture. However, what we (and the original research) highlighted was missing from such comparisons was biodiversity (see question above) and soil fertility impacts.

Soil fertility of course forms a critical component to future food security. Still, we have found little concrete data on large-scale (that goes beyond very localised studies) trends in soil fertility. How has global, regional or national soil fertility changed over the long-term and in recent years? Are there meta-studies which compare the relative impacts of different agricultural approaches on soil fertility?