Answer
$0.2\%$
Work Step by Step
The margin of error of a sample size $n$ is a $95\%$ probability that a sample lies within the margin of error which is $\pm\frac{1}{\sqrt n}\cdot 100\%$
Hence here the margin of error: $\pm\frac{1}{\sqrt {5000}}\cdot 100\%\approx\pm1.4\%$. Thus it improved the margin of error by $1.6-1.4=0.2\%$
