Opinion
Because there is less prosecution for atheists these days. Less pressure from the government and families to believe in a certain doctrine (although there is still pressure in some places). Also, communism instated Atheism as the state religion, seeing as how Marx described religion as the opiate of the masses. Lastly, with science some people feel that mysticism no longer has a place in their lives since everything has a rational explanation.
Opinion
Everything in the first answer is true, though I think it is prudent to note that the biggest reason is probably science. Deities are usually put in place to explain things that couldn't be explained at the time (Zeus was the reason for lightning, for example). Now that we have an explanation for lightning, we no longer need Zeus.
At this point, god has been relegated, by anyone who understands enough science, that the only place for him anymore is untestable areas with assertions about God making the Big Bang happen and having a heaven/hell to go to after we die. We now know a deity is not needed to make a star, planet, life, sentience, and other major things previously attributed to him/her. So, logically at this point god can only be a "clockmaker" who started the universe via the Big Bang and hasn't interfered since (which makes him negligible), or simply doesn't exist. Either would give the same amount of evidence we have today: none.
As science continues to progress, there is less and less need for God (as shown in the previous paragraph, he's nonexistent or negligible already), and with advancements in global communication, polling studies, and such it becomes more an more apparent that organised religion is generally a corrupting influence that is a detriment to society.
All religions are decreasing. More people are becoming atheists, agnostics or just not sure about religion
If by "most atheists", you are referring to the entire world, the population of atheists in China dwarfs the rest of the world's atheist population. Most Chinese Atheists adhere to a combination of Confucian and Materialistic philosophical principles.If by "most atheists", you are referring to Western Atheists, such as those in Europe and Anglo-America, these Atheists adhere to Rationalist Skepticism or Humanism as philosophical principles.
Their population is Increasing slowly
Increasing human population Urbanisation of the population Increasing human Agriculture Increasing use for Hydroelectric Increasing use in Industry.
increasing
population is increasing
Subject: The population of the US Predicate: is increasing
The population of New York City is increasing.
Canada's population is increasing. Right now, it is increasing one unit every minute and 27 seconds.
It is increasing by 100 a day
Yes, by protecting the habitat and captive raising of pandas the population is slowly increasing.
increasing because in Oregan, there is no tax