The landscape of longitudinal research today

This volume has presented examples of world class longitudinal research with policy and programme relevance. They join a growing number of researchers working with longitudinal data. In the last ten years, the number of publications citing use of longitudinal data has grown by 75%, shown in Figure 9.1. This growth presents an important resource for policy makers and practitioners towards meeting their sustainable development targets.

Despite the innovations presented, the potential relevance and impact, it is no doubt that longitudinal researchers today have experienced challenges in their dedication to this type of work.

To further unpack the landscape of longitudinal research, a systematic analysis of 122 longitudinal studies was conducted (Banati, 2019). A comprehensive search of the published literature was undertaken in Google Scholar, Pubmed and Scopus using the following search terms: birth cohort, longitudinal, child, life course and life stage. The study also drew from the largest open source database of longitudinal studies available – the Low and Middle Income Longitudinal Population Study Directory developed by the Institute for Fiscal Studies (2018). Inclusion criteria were (1) a minimum of two rounds of data collection; (2) first round conducted after 1970; (3) capturing information and responding to questions relevant for children. The studies are located in high-, middle- and low-income countries. Without a doubt, this was not an exhaustive process and may not have captured all available studies. Despite this, to our knowledge, we have identified and analysed the largest collection of longitudinal studies among children to date.

In addition, an online survey was created and shared with UNICEF's GLORI network members and additional investigators identified from the systematic analysis. GLORI – the Global Longitudinal Research Initiative – is a research network of longitudinal researchers working on topics relevant for children. It has 31 members working in 41 countries. The membership list can be found on the GLORI website (UNICEF, 2020). These were largely observational studies (61%). Most studies (63%) had more than five years of data collected, the average attrition rate was 19.8%.

Challenges experienced by longitudinal research today

The results of our examination of studies indicate that good longitudinal research is costly, and funding tends to be secured by wave and through multiple donors, with differing priorities. Only 13% of studies were identified as funded by national (governmental) entities, raising questions of sustainability.