Voting on EOS is incredibly important. Active voting makes this platform safe and efficient so there's no surprise that the platform is designed the way that encourages the EOS community to cast new votes. If someone doesn't cast new votes, the latest vote of this person gradually loses its power.
What's the Purpose of the Vote Decay?
In May 2018 Block.one enabled a new feature on the EOS platform —
vote decay. “In order to maintain maximum voting influence, each voter will have to re-assert their vote every week. Voting influence decays with a half-life of 1 year for those who do not keep their votes up to date.”
The move was inevitable because many community members were uneager to cast new votes. They have voted for some block producer candidate at some point and this vote still counted each voting period. As a result of such negligence, some inactive BP candidates still had new votes every election. This situation made no sense. That's why the vote decay was a necessary update.
Formula
If we care about mathematical accuracy the votes don't literally decay. What actually happens is that the newer votes have larger voting weight than the old ones. The effect is the same, but technically it is achieved differently. Below you can see the formula:
Since 01/01/2000 the EOS.IO software utilizes seconds for block_timestamp_epoch. In a more accessible way this formula can be presented this way:
The value of weight:
The formula means that the vote can gain some weight only once a week or less often. Voting at 00:00:01 UTC on Saturday once a week is the best way to perform the highest voting power. It is also necessary to stake and unstake tokens while casting new votes. Weekly revoting increases the weight of the vote by around 1.34%. When thousands of the EOS community members vote actively this small increase of voting power becomes significant and it influences the outcome of the voting and the rewards spread among the 21 Block Producers. The relevancy of votes shouldn't be underestimated.
Proxy Voting
In the case when a user delegates his/her voting power to a proxy voter the need to re-assert (or change) the vote is as important as in the case when the user votes her/himself. Updating the delegated voting power might be presumed even more important because the recast of the vote ensures that the user still trusts the proxy voter and proxy voter is doing everything right.
The Vote Decay's Effect on the Results
EOS Authority’s Voting Decay Analysis is tracking the summary of the decay of the voting weight of the EOS platform. That's the easiest way to see what effect the vote decay has on the network.
Those interested in their personal current strength of vote can check it in their accounts on eosq. The Votes tab provides all the needed info on the subject.
The annual vote decay equates to 50%. It doesn't seem too much but on a scale of the entire community such decline of numerous votes can seriously affect the voting outcome resulting in changes brought by the new elected Block Producers. The mission of Block Producers is to act in accordance with the interests of the voters so wise and timely voting is something that makes EOS good for users.