What is app store conversion rate?

WITH daily AS (
  SELECT
    store,
    app_id,
    date_trunc('week', metric_date) AS week,
    SUM(impressions) AS impressions,
    SUM(product_page_views) AS page_views,
    SUM(first_time_installs) AS first_time_installs,
    SUM(redownloads) AS redownloads
  FROM app_store_daily_metrics
  -- Both stores restate recent days. Cut the unstable tail or every
  -- Monday review will show a fake decline.
  WHERE metric_date < CURRENT_DATE - INTERVAL '3 days'
  GROUP BY 1, 2, 3
), rates AS (
  SELECT
    store,
    app_id,
    week,
    impressions,
    page_views,
    first_time_installs,
    redownloads,
    100.0 * page_views / NULLIF(impressions, 0) AS view_rate_pct,
    -- First-time installs only. Re-downloads are returning users and
    -- belong in a retention view, not in an acquisition conversion.
    100.0 * first_time_installs / NULLIF(page_views, 0) AS conv_pct
  FROM daily
)
SELECT
  week,
  store,
  app_id,
  impressions,
  page_views,
  first_time_installs,
  redownloads,
  ROUND(view_rate_pct, 2) AS impression_to_page_view_pct,
  ROUND(conv_pct, 2) AS page_view_to_install_pct,
  ROUND(conv_pct - LAG(conv_pct) OVER w, 2) AS conv_change_pp,
  -- 4-week trailing mean smooths feature placements and paid bursts.
  ROUND(AVG(conv_pct) OVER (
    PARTITION BY store, app_id ORDER BY week
    ROWS BETWEEN 3 PRECEDING AND CURRENT ROW
  ), 2) AS conv_pct_4w_avg
FROM rates
WINDOW w AS (PARTITION BY store, app_id ORDER BY week)
ORDER BY store, app_id, week;