*3.3. Classification by Years*

Figure 7 shows the period of time in which RULA has been used and in which areas of knowledge.

**Figure 7.** Number of studies classified by knowledge and year categories: Agriculture, forestry and fishing (**A**); Mining and quarrying (**B**); Manufacturing (**C**); Water supply; sewerage, waste management and remediation activities (**D**); Construction (**E**); Wholesale and retail trade; repair of motor vehicles and motorcycles (**F**); Transportation and storage (**G**); Accommodation and food service activities (**H**); Information and communication (**I**); Financial and insurances activities (**J**); Professional, scientific and technical activities (**K**); Administrative and support service activities (**L**); Public administration and defiance; compulsory social security (**M**); Education (**N**); Human health and social work activities (**O**); Arts, entertainment and recreation (**P**); Other service activities (**Q**); Activities of households as employers; undifferentiated goods and services producing activities of households for own use (**R**); and Other scopes not previously included (**S**).

The RULA method was created in 1993; however, according to the review carried out, it was not until 1998 that it was first applied.

From 1998 to 2019, the method has been applied every year. It should be noted that the year 2019 includes only the studies developed up until April.

The year 2016 stands out for the largest number of research studies (32). This is followed by the year 2018 with 28, 2017 with 26, 2012 with 22, 2014 and 2015 with 19 each, 2013 with 17 and 2010 and 2011 with 11 each. All other years have 10 or fewer studies.

Over the past 10 years, there has been an increase in such research. This may be due to the importance and awareness that occupational hazard prevention has received in recent times. In addition, it might be linked to the development of new technologies. These allow the method to be applied more quickly and efficiently (Figure 7).

It is noted (Figure 7) that over the past 10 years, the number of categories investigated has also increased compared to the previous 12 years. The year 2016 is characterised not only as having the largest number of publications, but also by the largest number of areas studied (11). "Manufacturing" stands out for representing 13 of the 32 research studies, followed by "Human health and social work activities" with 6. There are seven years with a single category (1998–2002, 2004 and 2006).
