Used to live in Polk County. The assessor watches new listings in the MLS so they can raise assessments as soon as possible even if your house doesn't sell right away.
Now live in Columbia, MO. Missouri does not allow sale prices of real estate to be publicly disclosed. As a retired banker & realtor, I find this to be ridiculous. However, real estate taxes are lower & stable. My real estate taxes have increased only $211 in four years. State income taxes are also lower in Missouri & the weather is much better. However, sales tax is 5.6% on food & 8.6% on everything else.