Сезонность CTR по источникам рекламы по месяцам

SQL, по которому посчитано

WITH monthly AS (
    SELECT
        date_trunc('month', date) AS month,
        source,
        sum(clicks) AS clicks,
        sum(impressions) AS impressions
    FROM ads
    WHERE date >= (
        SELECT date_trunc('month', max(date)) - INTERVAL '11 months'
        FROM ads
    )
    GROUP BY 1, 2
)
SELECT
    month,
    round(
        sum(CASE WHEN source = 'Яндекс Директ' THEN clicks ELSE 0 END)::DOUBLE
        / nullif(sum(CASE WHEN source = 'Яндекс Директ' THEN impressions ELSE 0 END), 0),
        4
    ) AS ctr_yandex_direct,
    round(
        sum(CASE WHEN source = 'VK Реклама' THEN clicks ELSE 0 END)::DOUBLE
        / nullif(sum(CASE WHEN source = 'VK Реклама' THEN impressions ELSE 0 END), 0),
        4
    ) AS ctr_vk,
    round(
        sum(CASE WHEN source = 'Продвижение WB' THEN clicks ELSE 0 END)::DOUBLE
        / nullif(sum(CASE WHEN source = 'Продвижение WB' THEN impressions ELSE 0 END), 0),
        4
    ) AS ctr_wb,
    round(
        sum(CASE WHEN source = 'Продвижение Ozon' THEN clicks ELSE 0 END)::DOUBLE
        / nullif(sum(CASE WHEN source = 'Продвижение Ozon' THEN impressions ELSE 0 END), 0),
        4
    ) AS ctr_ozon
FROM monthly
GROUP BY month
ORDER BY month