The following bar chart shows total number of recorded bird strikes on aircraft for each year.
It is clear that the graph is going up from 1990 to 2014. Does this mean that a given flight now has a higher probability of suffering a bird strike than 20 years ago? The above data can't answer that question, we need more context. In this case we need to know the number of flights per year. It is possible that for some reason bird strikes are now more likely but it is also possible that the probability of a bird strike has dropped since 1990 but the total number of flights per year has significantly increased.