The graph indicates the average amount of money (in euros) that four distinct mobile phone companies charged per month between January and September 2002.
As can be seen, Sim TX had the fastest-growing service fee, although Domo largely led in prices. Lex slightly raised the charge, while Alpha generally stabilized its service cost.
Domo offered the most expensive monthly contracts, ranging from 15 to 25 euros, with the peak observed in July. Sim TX, however, was the business that provided the cheapest service for the first six months at about 5 euros. Only in July did it equal Alpha at 10 euros, and in September it exceeded the leading firm, Domo, at 25 euros, a fivefold increase compared to its initial fee.
Like Domo and Sim TX, Lex also charged more over time, but the increase was relatively small (7 euros) compared with the previous companies. In contrast, Alpha’s cost was quite stable, except for a slight rise of 4 euros between May and June, after which the amount returned to its normal level of around 10 euros per month.