Also most of the important numbers that the average person cares about such as inflation or unemployment are collected in a very rigorous way that is hard for a government officials to modify without leaving a damning paper trail. Not to mention the vast majority of private measures match up with these numbers.
These measures are by no means perfect. The unemployment rate has significantly over estimated the health of the economy since the great recession, but this isn't due to a conspiracy. It's caused because it systematically under counts people who have dropped out of the labor force, or are under employed. (This is for the most popular unemployment rate number, there are much better employment numbers to use that don't suffer from this issue.)