Deaths tend to be more accurate than just confirmed cases. One way to account for testing rates is to look at the test positive rate, and use that as a proxy.

Deaths tend to be more accurate than just confirmed cases. One way to account for testing rates is to look at the test positive rate, and use that as a proxy. If the test positive rate is 50% (as it was in Spain at some point), you can be pretty sure you’re missing a lot of cases. So if Spain has “600 cases” but only did 1200 tests, they probably have way more real cases than Germany’s “3000 cases” out of 30,000 tests. FWIW, Germany had 9 deaths on March 17, while UK had 10 deaths on March 14. By that metric, the UK led Germany by 3 days. There’s more to it than just the one national lockdown date — in particular, Germany is federal and I think different states went into lockdown at different times, as in the US. But meanwhile, South Korea and Taiwan have avoided lockdowns entirely, so it’s clearly not only about lockdown timing — availability of testing, as in Germany, helps a lot with keeping the sick isolated.