Online petitions and parliamentary debate: How do UK parliamentary petitions grow over time?

This is the first of two Insights on UK parliamentary petitions, which examine how petitions grow over time and how geography influences their growth.

Petitions have a long and chequered history as a tool to influence policymakers in parliamentary democracies. An early example is the 1783 Quaker Anti-Slavery Petition, which ultimately succeeded in 1833 when slavery in the British Empire was abolished under the Slavery Abolition Act.

In recent years, with the advent of online petitions, there has been a resurgence in the use of petitions. This has been encouraged in part by the promise of a government response for any petition reaching over 10,000 signatures and a possible parliamentary debate for any petition reaching over 100,000 signatures.

In this Insight, by tracking the hour-by-hour growth of all petitions from July 2015 to November 2018 on the petition.parliament.uk website, we examine the reasons why some petitions grow virally, collecting hundreds of thousands of signatures, while others fail to gain even modest support.

How do petitions grow?

The graphs below show that no matter how successful a petition is, for the majority, growth is represented by an s-shaped curve. This is characterised by very slow growth at the beginning, a period of rapid growth (spanning a few days) followed by a flattening of growth. Some petitions have multiple s-shapes, but very few petitions have a gradual growth to success spanning weeks.

In figure 1 below, 1a plots the growth of 20 unsuccessful petitions which did not meet the 10,000 signature threshold needed for a response by the Government.

1b plots the growth of 20 petitions which met the threshold for a Government response but did not meet the 100,000 signature threshold for consideration for debate..

1c plots 20 petitions which exceeded the 100,000 signature threshold for debate.


Three line graphs showing the growth of failed petitions, petitions with a Government response and petitions debated.
View larger image

How many petitions reach the threshold?

The figure below plots how many petitions (since July 2015) gained a given number of signatures, as denoted by the x-axis.

The red line marks the threshold for petitions which received enough signatures for a written Government response. The blue line denotes the threshold for petitions which received enough signatures to be considered for a debate in the Commons.

A histogram showing the number of signatures for all past petitions. It shows the dip before a petition hits the 10,000 and 100,000 signature mark, followed by a bump to get it over the line.

It’s interesting to note that there is a marked dip in the number of signatures before the 10,000 signature mark and a bump just over the 10,000 signature mark. The same happens at the 100,000 signature mark. This suggests that once a petition nears the 10,000 or 100,000 threshold there is a public push to drive it over the threshold.

There also seems to be a sharp step at around 150 signatures, suggesting once a petition has 150 signatures it has a far better chance of succeeding. The exact reason for this is not clear, but could be related to ‘Dunbar’s number’. The anthropologist Robin Dunbar suggested humans can only sustain stable relationships with around 150 people. This could suggest that if a petition is of interest to more people than just your circle of acquaintances, it has an increased chance of succeeding. However, over 99.3% of petitions do not reach the threshold for a response by the Government and only 0.09% reach the threshold for a possible debate.

Indicators for a successful petition

During the period analysed (July 2015 to November 2018), the seven petitions which received the most signatures were:

Petitions with only around 100 signatures included the following:

From this we can conclude that successful petitions seem to:

  1. Have a simple message.
  2. Be related to broad national topics which resonate with a wide spectrum of society, and therefore have a large pool of people potentially willing to sign it.
  3. Have some level of emotion associated with them.
  4. Ideally be related to a topic which is already in the national eye through media exposure.

In contrast, petitions with only around 100 signatures seem to be on more specific points which resonate with fewer people. For example, the petition Keep the A422 through Farthinghoe closed and build a sensible bypass instead was unlikely to reach the threshold for debate as only 413 people live in Farthinghoe (according to the 2011 Census). However, the exact reasons any given petition succeeds or fails are complex and to some extent based on luck and timing. For example, a petition which gets media exposure, or is shared by someone on social media with many followers, will have a higher chance of succeeding.

One may think the petition, Take freight off our roads and onto an improved Railway Freight system would attract more mainstream attention, as it is part of Government policy. But this petition may have been unsuccessful as people are less likely to be emotionally attached to this topic, or just simply that it never got the media attention it needed to grow.

In the next Insight we will examine how public engagement with petitions differs across the different regions of the UK.


Note: This Insight was updated on 23 August 2019. An earlier version stated that the 1783 Quaker Anti-Slavery Petition was the first recorded petition submitted to the UK Parliament. In fact it common was to submit petitions during the medieval period and particularly after the 1640s.


About the author and fellowship: This is a guest post by Dr Roderick MacKenzie, an Assistant Professor in the Faculty of Engineering at The University of Nottingham. Dr MacKenzie is currently undertaking a fellowship with POST, exploring how data science research methods can help the House of Commons Library.


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