The line graph shows the changes in oil prices per barrel from 1973 to January 2009.
Overall, oil prices increased over this period, but they fluctuated a lot. In the 1970s, prices rose sharply, reaching around $40 per barrel by the late 1970s. During the 1980s and 1990s, prices generally fell and remained relatively low, mostly between $15 and $30 per barrel, with small ups and downs.
From the early 2000s, oil prices started to rise steadily. This increase became very sharp after 2005, and prices peaked at around $140 per barrel in 2008. However, after this peak, there was a sudden and significant drop, and by January 2009 the price had fallen to about $40 per barrel.
In summary, the graph shows long-term growth in oil prices with major fluctuations, including a dramatic rise and fall near the end of the period.