Step 1: Find increase.
\[
\text{Increase} = 5,00,000 - 4,00,000 = 1,00,000
\]
Step 2: Calculate percentage change.
\[
%\;Change = \frac{\text{Increase}}{\text{Original value}} \times 100
\]
\[
= \frac{1,00,000}{4,00,000} \times 100 = 25%
\]
Step 3: Conclude.
Therefore, the percentage change is 25%.
Final Answer:
\[
\boxed{25%}
\]