Growth of Airbnb_LAG

Growth of Airbnb
Estimate the growth of Airbnb each year using the number of hosts registered as the growth metric. The rate of growth is calculated by taking ((number of hosts registered in the current year - number of hosts registered in the previous year)/the number of hosts registered in the previous year)*100. 
Output the year, number of hosts in the current year, number of hosts in the previous year. and the rate of growth. Round the rate of growth. Round the rate of growth to the nearest percent and order the result in the ascending order based on the year. 
Assume that the dataset consists conly of unique hosts, meaning there are no duplicate hosts listed.


SELECT  year,
		current_year_host,
		prev_year_host,
		round(((curent_year_host - prev_year_host)/(cast(prev_year_host AS numeric)))*100) estimated_growth
FROM	
	(SELECT year,
			current_year_host,
			LAG(current_year_host, 1) over (ORDER BY year) AS prev_year_host
	FROM
		(SELECT extract(year
						FROM host_since::date) AS year,
				count(id) current_year_host
		FROM airbnb_search_details
		WHERE host_since IS NOT NULL
		GROUP BY extract(year
						FROM host_since::date)
		ORDER BY year) t1) t2