Line graphs are commonly used to show how the value of something changes over time or to compare how several things change over time relative to each other. They are useful in creating visual representations of changes in values over time, including changes in the prices of securities, company revenue sheets, and histories of major stock indexes. Line graphs are also helpful in allowing the user to visualize trends, which can greatly aid in analyses. They are commonly used in finance, but can also be used in other fields for different purposes. Line graphs are simple, easy to understand, and efficient, making them a common and effective chart type. They are best used when tracking changes over short and long periods of time, and when smaller changes exist. Line graphs are not necessarily the best choice for displaying quantities of things, working with categorical data, making part-to-whole comparisons, or showing sparse data sets.