‘Pressure groups are voluntary organisations formed to advance or defend a common cause or interest.’ They do not strive to take office or to govern; they simply seek to express their ideas in an organised manner. There are several ways in which they try to raise awareness: ‘from passing information to passing letters of protest, from having informal consultations to staging popular demonstrations.’  Pressure groups are very diverse in terms of their agenda, what type of agenda do they actually have? Who do they seek to influence? Do they have a broad agenda? Also, their size membership is another factor which sets them apart, this portrays how successful they actually are, the bigger the pressure group the more influence they will have. Finance is another aspect which shows the mixture of pressure groups. How do they get their money? This helps determine whether a pressure group is politicised or not.
Moreover, there are different types of pressure groups which completely set them apart from one another. First of all, you have sectional pressure groups; they represent a particular section of the society. They have leverage with trade unions or political parties. They go more along the corporate lever as they are considerably politicised. Cause or promotional pressure groups are ones that ‘seek to promote the beliefs, ideas and values in which their supporters believe, but these are not ideas which are of benefit to their membership, other than in a most general sense.’  They tend to put forward ideological causes to support, they’re less entrenched. You also have oppositional pressure groups that tend to oppose government policy, such as the student protests or any other protest groups. Oppositional pressure groups are likely to be more permanent. Informative pressure groups are ones that provide and gather information to make people informed about particular issued. Lastly, you have the commentator pressure groups; ‘respected and authoritative commentators on particular areas of policy.’  They’re formed by people who have knowledge, tend to affect the government a lot as they’re institutions and academies.
Similarly, you’ve got social movements. Pressure groups can become or be a part of a social movement; however a social movement is much broader. For example, the Greek strikes; at first it was just a protest, but once it was broadly accepted, so broadly that it then became a movement. Another distinctive example is the labour movement in the 70’s. Social movements do not seek office in theory, however their goal is to influence policy, influence economic agendas or to strongly campaign or lobby for an issue.
Furthermore, pressure groups can be an advantage to democracy as it introduces a form of toleration which enables us to achieve reciprocity. It exposes us to ideas that we do not necessarily agree with. Pressure groups bring forth ideas and changes which is not the norm, this enhances the idea of pluralism; it allows them to express their ideas and allow diversity, it secures independence from the community. Also, pressure groups allow power to be dispersed. For example, in the UK you have got two very powerful parties; pressure groups help to disperse their powers. Lastly, pressure groups boost participation within the democratic system. They increase participation in the democratic process on a variety of different levels. However, pressure groups can also be a bad thing for democracy. Politicization is the main argument against groups fostering democracy. Is it really okay to put forward democratic policies through an undemocratic way? It seems as if they’re sort of cartels of interest, a bunch of privileged groups that just benefit. Also, it burns the bridges because pressure groups seem to undermine the mandate of elections. People do not vote for a group but for a party. Elections should be clear cut.
Additionally, too much division creates instability. Society has a collective goal, so if you have got individual members creating different groups, this then undermines the collective goal. Too many decision makers make it difficult to come to an overall agreement. Going back to the rational choice theory, people will act in a way to maximise their profit. They seek to promote their own self-interest. So, even though your best option is to share, you are not going to because you might lose it all. The resource mobilization model theory suggests that ‘the entrepreneurial-organizational variant of this approach even allows for the possibility that grievances and discontent may be defined created and manipulated by political entrepreneurs and organizations.’ 
As Mancur Olsen explains, ‘Collective action is individually irrational. Individuals promote self-interest, not the group’s interest.’ It is all about self-interest for the organisations, as explained by the game theory and prisoner’s dilemma. This suggests that collective action problems mean that pressure groups can harm democracy. As they only have their own interest, if they benefit from it, that is all what matters even if it puts others at a disadvantage. For example, ‘$4 million lobbying campaign a football team put together seeking taxpayer spending for a football stadium to a mere $20,000 that opponents of the spending were able to raise.’  ,’The few who will benefit from the transfer have an easy time organizing to lobby for it, while a group as diverse and dispersed as taxpayers face what Mancur Olson called a collective action problem.’  This creates instability and unfairness within the democratic process because it leads to a group being more powerful than the other because of the unequal distribution of money and resources. So the minority, a certain part of the population can have an unequal influence against the majority which creates unfairness and undermines democracy this is considered to be a collective action problems because powerful insider groups can use their insider status and power to go and pursue their own personal cause. For example, ‘There is a danger that ministers may be prepared to accept too uncritically the advice of powerful interest groups. They may accede to the requests of those groups that can afford to present their case most effectively, even if there are substantial objections to what they propose.’ 
On the other hand, collective action problems don’t necessarily mean that pressure groups can harm democracy. As there are a variety of cases where pressure groups have actually enhanced democracy and have not resulted into any collective action problems. For example, ‘it allows individuals to associate with one another and proclaim their views, essential rights in any democracy.’  Pressure groups ‘provide a safety valve enabling any person with a grievance to feel that he or she is able to vent their disenchantment.’  This allows minorities who feel ignored to speak out and be heard. Such as, ‘Fathers for Justice’ which is a pressure group that seeks for fathers’ rights. Another reason why pressure groups enhance democracy and do not harm it is because they limit government, ‘groups check government power and, in the process, defend rights and freedom.’  These functions are just a few of many that show pressure groups do actually enhance democracy rather than harm it.
However, it is not only collective action problems that mean pressure groups harm democracy. Pressure groups have other issues which directly affect democracy. For instance, it creates political inequality. ‘Pressure groups tend to empower the already powerful. They therefore increase rather than reduce, political inequality.’ This has a negative effect on democracy itself as it contradicts the whole concept of democracy and it allows those who have access to resources to impact decisions.
Even though there are many factors which lead to the fact that collective action problems do mean that pressure groups harm democracy. It is not always the case, as there are also various other reasons which lead to pressure groups affecting democracy in a bad way, such as the ones I mentioned before. Nonetheless, there are also a variety of cases that suggests pressure groups enhance democracy on countless levels. It really depends on the pressure group itself and its aims, what audience it’s trying to reach and what it is actually trying to achieve. If they’re politicised and have a huge influence on decision making or if they just seek to promote ideological beliefs and are less entrenched. Therefore, collective action problems are just a part of a wider range of factors which result from self-interested pressure groups that are in it for their own benefits, which results into the destruction of democracy. Nevertheless, this is not necessarily always the case as pressure groups do tend to bring about positivity to democracy.
In conclusion, it all depends on a pressure groups agenda, and what their intentions are.