Measuring Legislative Complexity

Data as at 12 Dec 2022

Legislative complexity is a growing challenge across the Commonwealth statute book. This page demonstrates how the complexity of Commonwealth Acts made since 1901 can be explored quantitatively.

The page prompts questions such as:

  • Why have cross-references between Acts become so common and why do particular Acts become nodes in complex networks of cross-references? Is there an alternative to such extensive cross-referencing, or is this the best approach to law design?
  • Why do certain areas of lawmaking, such as corporations and financial services, have so many definitions, while others areas of lawmaking include fewer defined terms?
  • What are the consequences of the rapid legislative change present in the modern statute book, including for people who must comply with the law and those who make it?
  • Why has the vocabulary of the average Commonwealth Act grown so much over the past 120 years? Is this a desirable increase in the precision of language or a conceptual explosion in which readers must comprehend more complex prose?
  • What explains the rise of indeterminate terms such as those related to ‘reasonableness’ and ‘good faith’? What does this mean for the roles of courts and administrative decision-makers?

This page is based on the ALRC’s analysis in Complexity and Legislative Design. The page principally uses the As made Acts – Complexity and linguistic data and In force Acts – Complexity and linguistic data data sets. Columns related to cross-references, definitions, amendments per year, vocabulary, conditional statements, and various indeterminate concepts form the basis of the analysis. To identify the relevant columns, please see the Explanatory Note for these data sets.

Cross-references and defined terms

Legislative provisions can be deeply interwoven with one another through cross-references and defined terms. This kind of interweaving, where few provisions of an Act stand on their own, is a common symptom of complexity. Such interconnections mean that in understanding even one section of an Act a person may need to refer to dozens of other sections, both within the Act and across the statute book. These interactions are not always drawn to the reader’s attention, and nor are connections always structured logically.

Cross-references to other Acts

Figure 1 highlights the scale of legislative cross-referencing between in force Commonwealth Acts, with each line indicating a cross-reference and its width indicating the number of references. The size of each point represents the length of the legislation. As is clear in the Figure and following Figures, some Acts are central nodes in the Commonwealth legislative universe, with hundreds or even thousands of cross-references to and from their text. Almost all Commonwealth Acts refer to another Act, and several refer to dozens or even hundreds of Acts. For example, the Income Tax Assessment Act 1997 refers to 160 other Commonwealth Acts, while the Criminal Code Act 1995 refers to 156 other such Acts.

Figure 1: Cross-references between in force Commonwealth Acts

The scale of these interconnections can be significant. Figure 1 shows the number of times the ten most cited Acts are cited by other Acts, as well as the number of times these ten Acts cite other Commonwealth Acts. The Income Tax Assessment Act 1997, for example, refers to another Commonwealth Act on 7,158 separate occasions. The Corporations Act 2001 refers to another Commonwealth Act more than 1,534 times, and is in turn referred to 4,658 times.

In total, Commonwealth Acts refer to other such Acts on 133,537 occasions.

Figure 1: Cross-references to and from the ten most referenced Acts

The approximate number of internal and external references appearing in as made principal Acts has fluctuated significantly from year to year, but has generally remained very high since the 1970s and particularly since the 1980s. Despite the narrow search criteria used to identify potential cross-references, the data generated to create Figure 2 still somewhat overestimates the number of internal and external cross-references. However, the trends and the changes in magnitude nonetheless provide clear evidence of increased use of cross-references. Moreover, the take-off in cross-references in the 1970s more broadly mirrors the rapid growth of Commonwealth lawmaking during and after this decade.

Figure 2: Internal and external cross-references in as made principal Acts

Legislative definitions

Approximately 49,039 definitions appear across all in force Commonwealth Acts, and approximately 13% of all words in these Acts are potentially affected by a definition. Figure 3 shows the number of definitions that appear in Commonwealth Acts, classified according to the subject-matter of the Act in which the definitions appear. The top ten subject areas in the Figure contain 72% of all definitions that appear in Commonwealth Acts.

Figure 3: Number of definitions in Commonwealth Acts by subject-matter

As Figure 4 shows, definitions remain a persistent and significant feature of Commonwealth lawmaking, with many definitions being contained in new principal and amending Acts annually. However, the number of definitions being added to the statute book annually since 2015 is significantly less than in the previous decade.

Figure 4: Number of definitions in as made Commonwealth Acts annually

Legislative change

Legislative change is an inherent and desirable feature of legislation. But change also has consequences for the complexity of legislation. The statute book is ‘an ever-evolving network of complex information that expands organically and is extremely difficult to map’.1 This difficulty is exacerbated when legislation is amended with great frequency, and is particularly problematic when change occurs in a way that does not make clear how existing and new legislation fit together.2 Frequent amendment also results in changes to the existing ‘scheme structures’ which makes both the ‘legislative and procedural arrangements’ associated with the law more complex.3.

Frequent amendment arguably increases the risk that changes will be undertaken ‘without a review of existing provisions, or the legislation as a whole’, which the Commonwealth Attorney-General’s Department suggests can be a cause of complexity.4 Godwin, Brand and Langford note that patchwork legislative amendments result in an ‘inherent risk of incoherence’ that is only ‘exacerbated by legislation that is the product of continuing evolution over a long period of time’.5

As Figure 5 shows, the proportion of Commonwealth Act pages that appear in amending Acts has increased significantly over the past 120 years. More attention is paid to amending existing Acts than to establishing new principal Acts. The first amending Act was passed in 1903, reflecting the fact that the Parliament was occupied with making new principal Acts during the first two years of Federation. The pace of change to existing Acts has accelerated as amending Acts have become a focus of Commonwealth lawmaking.

Figure 5: Proportion of as made Commonwealth Act pages that are amending (1903–2022)

However, amendments to Commonwealth Acts are highly concentrated. Figure 6 plots every Commonwealth Act according to the the number of Acts amending it and the number of years it was in force. Blue points indicate Acts that are still in force, while yellow points represent repealed Acts. All Acts that have been amended by more than 200 Acts are labelled. As is clear in the Figure, amendments are focused on a selected number of Acts. Across all principal Acts, there is no correlation between the age of an Act and the number of amendments made to it. This suggests that amendments may be driven instead by other factors, such as the importance of selected legislation or subject-matter.

Among in force principal Acts, there is a moderate correlation between the age of an Act and the number of amendments made to it (0.27). But this could represent a form of ‘survivor bias’, in which the important Acts last a long time and accrue many amendments because they are important (rather than simply because they are old). The Acts that experience rapid and ongoing change through amendments are at greatest risk of incoherence, and the challenge of managing their complexity remains particularly important compared to more stable legislative schemes.

Figure 6: Number of Acts amending principal Commonwealth Acts based on their age