What does unemployment cost the employer?

When I collect Unemployment, what exactly does it cost my former Employer? I assume he has to pay something when that happens.
Each state charges the employer a percentage based on past experience. If the employer had no chargeable claims for the prior year, then the rate will be low. The state looks at total payroll vs total unemployment claims. The rate is charged on wages per employee up to a certain limit. Each state is different however, the minimum base is $7,000 a year.
Unemployment taxes are collected from an employer based upon the gross wage paid to all employees of the firm. The cost to your employer is reflected each year when the amount of unemployment collected by employees of that firm is tallied up. The upcoming year's assessment may well go up for the employer based upon how much unemployment compensation is collected against the firm's record.

Answers:
Not at the time of the claim. What happens is, what you pay in every year depends on your prior claims. The exact number varies by state, but if you have no prior claims in the past 5 years, you pay about 3% of your TOTAL payroll in unemployment. If you have claims, it can be anywhere from 7% of your TOTAL PAYROLL to 20% of your TOTAL PAYROLL, depending on your turnover.

So it can be significant.