Explanation:

- In 1994, 20% of the employees owned cell phones.

- In 1998, 60% of the employees owned cell phones.

- Calculate the increase in ownership: 60% - 20% = 40% increase in percentage points.

- To find the percent increase, divide the increase by the original percentage: $\frac{40\mathrm{\%}}{20\mathrm{\%}}=2$.

- Convert the result to a percentage: 2 * 100% = 200%.

- This shows a 200% increase in the fraction of employees owning cell phones from 1994 to 1998.

Correct Answer: Option 4: 200%