Binary Search Symbol Table
In computation, time consume depends deeply on the algorithm we choose. Since the search time consumes log2(N) and insertion  time consumes N/2, the insertion time increases sharply as compared to the search time. The only thing is that they depend on size of the symbol table, not the initial size because insertion and search time depend on the actual size of data set.

The chart below shows Percentage of Insertion Time over Search Time in your case.