Change in political participation over the last 40 years

Over the past 40 years the turnout of almost all of the general elections going down gradually yet noticeably, the turn out of the election in 1984 was 79%However in the most recent election in 2010 you turnout was considerably lower at 60%
But why has this been happening as due to the gradual decline in voter turnout there can be no clear reason found.
A reason for the lack of voters has been suggested to have been the fact that people are losing interest in politics and also feel that they have no voice and that their votes wont count for anything, a table found on http://www.exeter.ac.uk/media/universityofexeter/research/microsites/epop/papers/Henn_and_Foard_-_Young_People,_Political_Participation_and_Trust_in_Britain.pdf shows that in a recent survey that was taken 31% of the people asked believed that voti55555ng in a general election was not effective to the government.
Further more, a larger 40% of the people asked though that local elections were also ineffective.
Supporting this theory even more another survey was taken in which statements were issued and the public were asked if they agreed/disagreed, one of the statements was “By voting/ if I voted, I feel as if I can/ could really help to change the way that Britain is governed” the result of the statement was 44% of the people asked disagreed, meaning that it is a large ideology from the public that the government don’t care for their opinions.
Using this statistic on the bigger scale of the whole of the UK, it is simple to see that a large portion of the population believe that voting wont effect the government.
This of course cant be the only reason that voter turn out is decreasing at such a rate.
Another reason for the lack of voter turnout has been considered as the fact that people have lost trust and belief in the MPS