This article is a part of my heavy metal lyrics project. If you’re interested in seeing the code, check out the original notebook. In the next article we’ll use machine learning to perform review score prediction from album review text. Below is an interactive historical map of metal artists and albums reflecting the analyses shown here (click here for full-size version).

Summary

Things we’ll do:

  • Implement a Bayesian-weighted-average scoring metric for comparing albums with differing numbers of reviews.
  • Look at what the Metal-Archives community considers the best and worst albums, bands, genres, and countries based on weighted-average album scores.
  • Compare the popularity of different metal genres around the world.
  • Identify historical trends in heavy metal as told through album statistics and review scores.

Table of Contents

  1. Dataset
  2. Weighted-average album score
  3. Geographic distribution of albums and genres
  4. Global album trends
  5. Geographic trends

Dataset

The dataset consists of nearly 86,000 album reviews extracted from Metal-Archives (MA). Each review is comprised of a block of text and a score ranging from 0 to 100. The reviews cover about 35,000 albums produced by over 18,000 bands.

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Review traffic peaked around 2010 after a healthy rise throughout MA’s early years. Although the monthly rate has dropped since then, it’s held rather steadily since.

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A few things to note about the distribution of scores:

  • The distribution is very top-heavy, with an average of 78.5% and median of 81%.
  • There are peaks at multiples of ten and five because reviewers often round out their scores.
  • Over a fifth of the reviews gave scores of at least 95%, and nearly a tenth gave a full 100%.

Split dataset by album, band, genre, and country

For the upcoming analyses, I split the data in various ways.

By album

band_name name band_genre year review_avg review_num
1 Slayer Reign in Blood Thrash Metal 1986 84.75 44
2 Iron Maiden Iron Maiden Heavy Metal, NWOBHM 1980 85.58 40
3 Metallica Master of Puppets Thrash Metal (early); Hard Rock (mid); Heavy/T... 1986 80.64 39
4 Mayhem De Mysteriis Dom Sathanas Black Metal 1994 88.26 38
5 Iron Maiden The Number of the Beast Heavy Metal, NWOBHM 1982 86.55 38
6 Megadeth Rust in Peace Speed/Thrash Metal (early/later); Heavy Metal/... 1990 92.31 36
7 Black Sabbath 13 Heavy/Doom Metal 2013 67.81 36
8 Wintersun Time I Symphonic Melodic Death Metal 2012 68.39 36
9 Metallica Ride the Lightning Thrash Metal (early); Hard Rock (mid); Heavy/T... 1984 93.37 35
10 Megadeth Countdown to Extinction Speed/Thrash Metal (early/later); Heavy Metal/... 1992 77.06 35

Slayer’s Reign in Blood is the most-reviewed album, having been reviewed 44 times, with plenty of other famous classics making the top-ten.

By band

name genre review_avg review_num
1 Iron Maiden Heavy Metal, NWOBHM 80.94 480
2 Black Sabbath Heavy/Doom Metal 81.99 388
3 Megadeth Speed/Thrash Metal (early/later); Heavy Metal/... 74.94 357
4 Judas Priest Heavy Metal 78.94 328
5 Darkthrone Death Metal (early); Black Metal (mid); Black/... 79.47 289
6 Metallica Thrash Metal (early); Hard Rock (mid); Heavy/T... 72.11 281
7 Slayer Thrash Metal 74.72 273
8 Overkill Thrash Metal, Thrash/Groove Metal 79.04 248
9 Opeth Progressive Death Metal, Progressive Rock 78.55 244
10 Cannibal Corpse Death Metal 80.31 232

Aggregating over discographies, Iron Maiden is the most-reviewed artist. With 480 album reviews submitted, they stand well above the others.

By genre

This split in genres is a little different from the rest because there can be multiple genres per row.

genre review_avg review_num
1 death 78.53 27520
2 black 79.20 22283
3 thrash 77.42 14533
4 heavy 78.56 12576
5 power 78.62 11539
6 progressive 81.11 9355
7 doom 81.45 8923
8 melodic 76.99 8519
9 rock 77.07 7325
10 speed 79.41 4675

Death metal and black metal albums receive the most reviews, not surprisingly since they are the most popular genres in the dataset.

By country of origin

country_of_origin review_avg review_num
1 United States 77.49 25433
2 Sweden 78.82 8095
3 Germany 78.58 7745
4 United Kingdom 79.56 6760
5 Finland 78.32 4617
6 Norway 79.56 4398
7 Canada 78.67 3417
8 Italy 76.47 2571
9 France 79.24 2292
10 Netherlands 79.43 1775

The U.S. clearly leads the world in album production and reviews. There may be a slight U.S. bias in the data because it’s an English-speaking website, but the coverage of countries around the world is actually very comprehensive on Metal-Archives.

Weighted-average album score

Comparing albums by simply looking at average review ratings may not be the best way to gauge an album’s popularity (or infamy). This is important when the number of reviews per album vary dramatically. Just like looking at product reviews, when judging albums we naturally assign more weight to album review scores that are averaged from the experiences of many people.

As you can see below, there are plenty of albums on MA with only a single, 100% review. It doesn’t make much sense to say these albums are all better than the most popular albums. Likewise, there are plenty of albums with only a single 0% review. The same can be seen when splitting the data by band. I could apply a minimum number of reviews required to consider an album’s review score legitimate, but this shrinks down the dataset considerably and still weighs albums near the cutoff number and near the maximum equally.

Instead, I will use a weighted-average score that treats individual reviews for an album as “evidence” that the album ought to deviate from the population mean (of 79%). Ideally, this method would distinguish good albums based on them having many positive reviews, not just a handful. Likewise, it should help us reveal which albums draw a consensus of disdain from the MA community.

band_name name review_avg review_num
1 Beldam Still the Wretched Linger 100 1
2 The Extinct Dreams Фрагменты вечности 100 1
3 Pestilent Purgatory of Punishment 100 1
4 Ceremonial Castings Cthulhu 100 2
5 Sorhin Apokalypsens ängel 100 1
band_name name review_avg review_num
1 Patrons of the Rotting Gate The Rose Coil 0 1
2 Lotus Circle Bottomless Vales and Boundless Floods 0 1
3 Lost Souls Fracture 0 2
4 Waverly Hills The Nurse 0 1
5 Cloak of Displacement This Is the Only Way 0 1
name review_avg review_num
1 Pimentola 100 1
2 Sunken 100 1
3 Nebula 100 1
4 Dying Humanity 100 1
5 Dead Asylum 100 1
name review_avg review_num
1 The Ungrateful 0 1
2 Seventh Army 0 1
3 AIAA 7 0 1
4 Killer Fox 0 1
5 Dismembered Engorgement 0 1

Rating albums using Bayesian-weighted averaging

Supposedly IMDb rates content using the following weighted averaging scheme:

\[W_i = \frac{R_in_i + Cm}{n_i + m}\]

where \(R_i\) and \(n_i\) are average score and number of scores for a sample \(i\) (a movie in the IMDb case, an album in our case), \(C = \sum_{i=1}^n R_i\) represents the average of the full collection of scores, which I’ll call the population mean, and \(m\) is a tunable threshold for the number of ratings required to be included in the Top-250 list (25,000). (The page I linked uses \(v\) for “votes” instead of \(n\); I prefer this notation.) The issue with this is that it does depend on our choice of \(m\), which would have to be tailored to the dataset. One way to pick it is to choose some percentile of the album review count distribution. Choosing a high percentile would give a higher number for \(m\), weighing the second term in the numerator more heavily. This effectively gives more weight to the number of reviews, since a larger \(n_i\) is required to pull \(W_i\) away from the population mean \(C\). The choice of \(m\) therefore matters a lot, but it’s chosen subjectively. Ideally we should be weighing the population term in a way that reflects how confident we are that the population mean describes individual samples.

This weighted averaging is inspired by Bayesian statistics: the population parameter \(C\) represents a prior belief about an album’s true score, and the weighted average updates that prior based on the observations \(R_i n_i\). We can define a weighted average more rigourously if we fully adopt a Bayesian framework. Note that the album scores are distributed within the range 0-100, much like probabilities of a binary process (e.g. flipping a coin). Let’s say an album has some “true” score that the reviewers are estimating, like people guessing how likely a flipped coin will land on heads. We might have some prior belief about that how that coin might behave, based on our understanding of how coins typically land. We could then update that belief using our observations, arriving at a posterior estimate for the probability of landing heads. In the case of the album reviews, the scores can be anywhere in the range 0-100, rather than purely binary, but we’ll see that it doesn’t affect the math. We can follow the classic example of determining the posterior distribution for a Beta-Bernoulli model, in which we assume that the review scores for an album follow a Bernoulli distribution.

Let’s describe the population distribution of scores using the Beta distribution, using the population mean and variance to determine the appropriate \(\alpha_0\) and \(\beta_0\) parameters (see the “mean and variance” section of the wiki page). We can use this to represent our prior belief for the parameters of the model. Importantly, the Beta distribution is the conjugate prior for the Bernoulli distribution, meaning the posterior probability distribution is itself a Beta distribution. The posterior for an album \(i\) with \(n_i\) reviews and an average rating of \(R_i\) is a Beta distibution with the parameters

\(\alpha = s_i + \alpha_0\) \(\beta = n_i - s_i + \beta_0\)

where \(s_i\) is the number of sucessful trials (coins landing on heads), which in our case is the average review rating times the number of reviews: \(s_i = R_i n_i\).

The mean of a Beta distribution with parameters \(\alpha\) and \(\beta\) is given by

\[\mu = \frac{\alpha}{\alpha + \beta}\]

Thus we can define as our weighted-average score in terms of the sample and prior parameters:

\[\mu = \frac{R_i n_i + \alpha_0}{s_i + \alpha_0 + n_i - s_i + \beta_0}\] \[\mu = \frac{R_i n_i + \alpha_0}{n_i + \alpha_0 + \beta_0}\]

Doing the same thing for the prior mean \(\mu_0\) in terms of \(\alpha_0\) and \(\beta_0\), we get

\[\mu = \frac{R_i n_i + \mu_0 (\alpha_0 + \beta_0)}{n_i + (\alpha_0 + \beta_0)}\]

Look familiar? The prior mean is the same as the \(C\) parameter in the IMDb average, so the only difference between this formula and the other is that we now have a clear definition for the \(m\) parameter: it’s the sum of the Beta priors, which are directly derived from the population mean and variance!

\[\alpha_0 + \beta_0 = \frac{1}{\sigma_0^2} \left(\mu_0 - \mu_0^2 - \sigma_0^2\right)\]

To be fair it’s not obvious how this parameter behaves, but generally speaking a more narrow distribution of reviews in the broad population would yield a smaller variance \(\sigma_0^2\), which has a similar effect to using a larger \(m\) in the IMDb method. This is the expected behavior; a small prior variance represents a more confident prior belief about the mean. The key is that now we are allowing the prior variance to be based on the actual variance of the data, rather than simply picking a number.

Implementing this is straightforward: we just have to compute the prior parameters from the full dataset, then for each album use its average score and number of reviews to compute the parameters of the posterior distribution. From the parameters we then compute the posterior mean and call that our weighted average. Below are some examples of what the posteriors look like for some extreme examples where clearly the weighted average favors/punishes large sample sizes.

Examples

In these albums we can see the posterior probability distribution of each album compared to the prior, which is simply the population un-weighted average score distribution fit to a Beta distribution. The weighted average score is the mean of this posterior, computed independently for each album. Metallica’s Ride the Lightning has a raw average (sample mean) of 94%, which is less than the 100% of Nightmare’s Cosmovision, but the posterior mean of Ride the Lightning (91%) outranks that of Cosmovision (81%) due to its much larger sample size. Likewise, on the other side of the population mean, St. Anger’s 44% sample mean is better than the one 0% review of Boris’ Warpath, but the weighted average puts St. Anger at 49%, worse than Warpath’s 67%.

Apply weighted score to dataset

Weighted score distribution

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Looking at the histograms of the weighted average scores and raw average scores, we can see that the weighted scores push most samples towards the population mean. This is stronger when looking at albums since the sample sizes are generally smaller. In the case of genres and countries, the effect is quite weak and probably won’t affect rankings too heavily.

Best and worst albums

band_name name year band_genre review_num review_avg review_weighted
1 Entombed Left Hand Path 1990 Death Metal/Death 'n' Roll 25 97.76 93.81
2 King Diamond Abigail 1987 Heavy Metal 18 97.22 92.26
3 Katatonia Dance of December Souls 1993 Doom/Death Metal (early); Gothic/Alternative/P... 22 95.45 91.59
4 Bolt Thrower Realm of Chaos: Slaves to Darkness 1989 Death Metal 24 95.08 91.55
5 Symphony X The Divine Wings of Tragedy 1996 Progressive Power Metal 17 96.53 91.54
6 Morbid Saint Spectrum of Death 1990 Thrash Metal 23 95.00 91.36
7 Atheist Unquestionable Presence 1991 Progressive Death/Thrash Metal with Jazz influ... 21 95.33 91.35
8 W.A.S.P. The Crimson Idol 1992 Heavy Metal/Hard Rock 16 96.38 91.20
9 Suffocation Effigy of the Forgotten 1991 Brutal/Technical Death Metal 23 94.78 91.19
10 Primordial To the Nameless Dead 2007 Celtic Folk/Black Metal 13 97.54 91.18
11 Bathory Under the Sign of the Black Mark 1987 Black/Viking Metal, Thrash Metal 18 95.72 91.14
12 Metallica Ride the Lightning 1984 Thrash Metal (early); Hard Rock (mid); Heavy/T... 35 93.37 91.04
13 Ahab The Call of the Wretched Sea 2006 Funeral Doom Metal 20 94.95 90.90
14 Rush Moving Pictures 1981 Progressive Rock 15 96.20 90.83
15 Kreator Coma of Souls 1990 Thrash Metal 21 94.62 90.80
16 Riot V Thundersteel 1988 Heavy/Power/Speed Metal 15 95.87 90.60
17 Death Symbolic 1995 Death Metal (early); Progressive Death Metal (... 31 93.13 90.58
18 Acid Bath When the Kite String Pops 1994 Sludge/Doom Metal 17 95.18 90.55
19 Type O Negative October Rust 1996 Gothic/Doom Metal 16 95.44 90.52
20 Terrorizer World Downfall 1989 Death Metal/Grindcore 14 96.00 90.43

The best album by weighted-average score is the 1990 death metal record Left Hand Path by Entombed. Most of the top-20 albums hail from the 80s and 90s, a testament to their reputations as heavy metal classics. Primordial’s To the Nameless Dead and Ahab’s The Call of the Wretched Sea are the only post-2000 albums that make the top twenty.

band_name name year band_genre review_num review_avg review_weighted
1 Thrash or Die Poser Holocaust 2011 Thrash Metal 14 10.71 31.06
2 Hellyeah Hellyeah 2007 Groove Metal 13 10.69 32.11
3 Waking the Cadaver Perverse Recollections of a Necromangler 2007 Slam/Brutal Death Metal/Deathcore (early); Dea... 33 25.45 33.61
4 Six Feet Under Graveyard Classics 2 2004 Death/Groove Metal, Death 'n' Roll 10 7.50 34.12
5 Massacre Promise 1996 Death Metal 9 8.11 36.24
6 Grieving Age Merely the Fleshless We and the Awed Obsequy 2013 Doom/Death Metal 6 0.83 39.60
7 Six Feet Under Nightmares of the Decomposed 2020 Death/Groove Metal, Death 'n' Roll 11 19.27 40.13
8 Morbid Angel Illud Divinum Insanus 2011 Death Metal 30 35.43 42.58
9 Cryptopsy The Unspoken King 2008 Brutal/Technical Death Metal 18 31.00 42.83
10 Skinlab Revolting Room 2002 Groove Metal (early); Nu-Metal (later) 6 8.00 43.15
11 Machine Head Catharsis 2018 Groove/Thrash Metal, Nu-Metal 8 17.75 43.70
12 Dark Moor Project X 2015 Power Metal 6 9.50 43.90
13 Queensrÿche American Soldier 2009 Heavy/Power/Progressive Metal (early/later); H... 12 27.17 44.21
14 In Flames Battles 2016 Melodic Death Metal (early); Melodic Groove Me... 10 24.90 44.92
15 Celtic Frost Cold Lake 1988 Thrash/Death/Black Metal (early); Gothic/Doom ... 16 33.12 45.44
16 Aryan Terrorism War 2000 Black Metal 6 13.33 45.80
17 Machine Head Supercharger 2001 Groove/Thrash Metal, Nu-Metal 12 29.92 46.03
18 Six Feet Under Graveyard Classics IV: 666 - The Number of the... 2016 Death/Groove Metal, Death 'n' Roll 5 8.60 46.59
19 Bathory Octagon 1995 Black/Viking Metal, Thrash Metal 11 29.91 46.97
20 Huntress Spell Eater 2012 Heavy Metal 11 30.27 47.20

At the other end of the rankings, Poser Holocaust by Thrash or Die earns the worst weighted score, but Waking the Cadaver’s debut album Perverse Recollections of a Necromangler deserves a mention for having a whopping 33 reviews: it’s amusing that more people have reviewed this record than have reviewed Ride the Lightning. Maybe this just reflects on the sort of opinions album reviewers enjoy sharing…

Many of the bottom twenty albums actually come from fairly well-respected artists whose fans simply expected better. It almost seems like a rite of passage to disappoint your fans after a decade or two of consistent performance. Next we’ll look at which bands have done the best or worst over the full course of their careers.

Best and worst bands

name genre review_num review_avg review_weighted
1 Evoken Funeral Doom/Death Metal 32 94.94 91.80
2 Acid Bath Sludge/Doom Metal 27 95.07 91.44
3 Morbid Saint Thrash Metal 27 93.70 90.35
4 Moonsorrow Folk/Pagan/Black Metal 74 91.24 90.05
5 Intestine Baalism Melodic Death Metal 19 94.63 89.99
6 Type O Negative Gothic/Doom Metal 89 90.93 89.95
7 Demilich Technical/Avant-garde Death Metal 26 93.04 89.72
8 Satan NWOBHM, Heavy Metal 28 92.39 89.39
9 Forefather Black/Viking Metal 17 94.29 89.36
10 Angra Power/Progressive Metal 83 90.25 89.25
11 Solitude Aeturnus Epic Doom Metal 28 92.11 89.16
12 Gorement Death Metal 10 97.40 89.15
13 Repulsion Grindcore/Death Metal 17 94.00 89.15
14 Esoteric Funeral Doom/Death Metal 34 91.50 89.09
15 Primordial Celtic Folk/Black Metal 71 90.21 89.06
16 Kyuss Stoner Rock/Metal 38 90.74 88.66
17 Sabbat Black/Thrash Metal 21 92.29 88.55
18 Man Must Die Technical Death Metal 14 94.00 88.45
19 Wardruna Folk/Ambient 12 94.83 88.39
20 Impaled Death Metal 16 93.00 88.24

To accumulate a high weighted-average score, a band must put out many albums, each garnering many positive reviews. Many of the most popular bands in metal do poorly in this sense, as they set very high standards for themselves and almost always have one or two albums that far underperform compared to the rest of their discography. This leaves us with some surprise appearances at the top of the weighted-average rankings: Evoken takes the crown for highest weighted score. Over a six-album discography, they boast a minimum album rating of 91%. There’s quite a lot of variety among the top few bands, with many different genres and nationalities being represented.

name genre review_num review_avg review_weighted
1 Thrash or Die Thrash Metal 16 14.94 33.52
2 Skinlab Groove Metal (early); Nu-Metal (later) 17 17.35 34.47
3 Hellyeah Groove Metal 22 23.73 36.36
4 Waking the Cadaver Slam/Brutal Death Metal/Deathcore (early); Dea... 46 34.46 39.96
5 Legion of Thor Hardcore Punk/Metalcore (early); Death Metal/D... 7 3.86 40.01
6 Winds of Plague Symphonic Deathcore 33 37.24 44.07
7 Animae Capronii Black Metal 10 22.60 44.70
8 Grieving Age Doom/Death Metal 8 18.75 45.61
9 Car Door Dick Smash Thrash Metal/Grindcore 5 4.40 46.35
10 Aryan Terrorism Black Metal 6 13.33 47.26
11 Huntress Heavy Metal 14 33.43 47.74
12 Six Feet Under Death/Groove Metal, Death 'n' Roll 134 48.49 49.88
13 Damageplan Groove Metal 11 35.73 51.56
14 Mulletcorpse Brutal Death Metal/Grindcore 9 32.78 51.89
15 Enemy of the Sun Groove/Alternative Metal/Metalcore 6 24.17 52.33
16 Groza Black Metal 5 18.60 52.35
17 Propagating the Abomination Brutal Death Metal 5 21.20 53.45
18 The Great Kat Speed/Thrash Metal, Shred 14 42.29 53.69
19 Procer Veneficus Black Metal/Dark Ambient/Experimental Acoustic 12 42.00 54.72
20 Jewicide Raw Black Metal 4 17.25 54.97

Yet again Thrash or Die take up their position at the bottom of this ranking. It’s mostly due to that horrid debut album of theirs; it makes up 14 of their 16 overall reviews. Their 2015 follow-up album at least managed to get a couple of reviews over 40%…

Best and worst genres

genre review_num review_avg review_weighted
1 eastern 142 85.31 84.04
2 middle 125 85.28 83.87
3 grunge 147 84.42 83.32
4 post-metal 564 82.59 82.34
5 epic 1358 82.42 82.32
6 dungeon 55 84.51 82.09
7 synth 55 84.51 82.09
8 funeral 734 82.23 82.05
9 fusion 133 82.99 82.01
10 jazz 139 82.88 81.95

Interestingly, Middle-Eastern metal is rated very highly (it gets split up into “middle” and “eastern” because of the genre tag parsing). This chart has a lot of unexpected appearances, and I’m not sure there’s much to read into here. When grouping by genres there are far more reviews per sample, so the weighted averaging doesn’t stray far from the raw average.

genre review_num review_avg review_weighted
1 pop 83 62.80 65.89
2 nu-metal 534 65.94 66.40
3 deathcore 1007 66.88 67.11
4 acoustic 83 65.34 67.86
5 tribal 30 61.93 68.45
6 metalcore 1892 68.82 68.91
7 indie 18 61.44 70.09
8 groove 3703 70.12 70.16
9 cappella 16 60.94 70.32
10 cybergrind 12 58.25 70.47

At the bottom, no-one can be surprised to see pop music having lowest weighted reviews. Metal purists are known for the dislike of most deathcore, metalcore, and nu-metal, and it shows here as well.

Best and worse countries

Similar to genres, the large sample sizes of most countries seems to weaken the differences between the raw and weighted averages. Nevertheless the weighting brings up some interesting contenders for the best and worst countries when it comes to producing metal records.

country_of_origin review_num review_avg review_weighted
1 Ireland 280 83.01 82.49
2 Iceland 140 83.47 82.44
3 Denmark 962 82.49 82.35
4 Andorra 28 86.64 81.96
5 Tunisia 29 85.76 81.60
6 Singapore 100 82.37 81.26
7 Japan 1102 81.28 81.18
8 Jordan 33 84.12 80.99
9 Faroe Islands 71 82.24 80.84
10 Georgia 16 87.00 80.82
country_of_origin review_num review_avg review_weighted
1 Saudi Arabia 21 58.29 69.22
2 Ecuador 15 66.67 73.64
3 Vietnam 9 63.33 73.95
4 Algeria 10 65.60 74.27
5 North Macedonia 8 65.00 74.61
6 Iraq 5 60.40 74.79
7 Unknown 50 73.70 75.01
8 Syria 12 70.00 75.15
9 Botswana 14 71.43 75.38
10 Nepal 17 72.41 75.48

Geographic distribution of albums and genres

Now we’ll look at some geographic numbers describing the popularity of metal around the world.

Countries of origin

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  • The U.S. clearly dominates in album production (or at least the production of albums that are cataloged on MA; although I’m quite confident the selection bias is not too strong considering how active the MA community is).

  • Most of the top countries in the scene are European.

U.S. states of origin

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  • Within the U.S. itself, California produces the most metal albums, followed by a few other high-population states.
  • Normalized by population, Oregon and Washington produce the most; Pacific Northwest weather is perfect for heavy metal after all.

Top countries in each genre

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  • The U.S. is still the top producer of albums in most genres.
  • Italy is the only country to overtake the U.S. in any genre, outproducing the Americans in symphonic metal albums.
  • When it comes to the “melodic” genre tag, which most often refers to melodic death metal in particular, the Swedes and Finns contribute a large portion.
  • Germany produces a notably large portion of power metal albums.

Top genres in each country

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For most countries, death and black metal are the most common genres. The Ukranians seem to hold the strongest preference for a single genre, with nearly a third of Ukranian albums coming from bands identified as black metal. The largest stake power metal takes is in Germany.

Decline of top-rated bands

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As mentioned before, popular artists who have been around for a while often struggle to meet fan expectations as years pass. Here we see that eight of the ten bands that produced a top-ten album (based on weighted score) have seen overall declines in reviewer perception after a decade or two from their debuts.

Now for a more comprehensive look at the history of metal, as told by the MA community.

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  • The number of metal albums released per year grew up until the late 2000’s, but has since plateaued.
  • The annual average of weighted-average scores (fourth plot) stays quite high throughout the 70s and 80s, about the same time that many of the all-time top bands were releasing their most iconic albums.
  • As the metal scene saturated, quality dropped, with scores hitting a low point coinciding with the peak in number of albums.
  • Albums from the past decade, however, have performed better, with the average just about returning to pre-90s levels last year, giving fans reason to be optimistic about the direction that heavy metal is going.
  • Even the slump in album production in 2020-21 has not manifested in a drop in scores, indicating that the COVID-19 pandemic has not adversely affected the quality of metal albums!
  • The number of reviews per album is still in decline, but at least for albums of the past few years this is likely just due to recency bias. We saw at the beginning that the rate of reviews submitted to MA hasn’t actually dropped in recent years.

Yearly album output and review scores by genre

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Although most genres contributed to the rise of metal in the 2000s, black and death metal dominated the upward trend. Before then, it was heavy metal and thrash metal that ruled supreme, spearheading the 80s upswing that brought heavy metal into the public spotlight.

Early doom metal (led by Black Sabbath) is very highly rated, and even more recent doom metal albums continue to outperform material from other genres rather consistently. Early black metal albums likewise had a high-scoring start, but have mostly converged towards the overal average since then. Death metal did well in the early nineties, followed by a long brutal decline throughout the 2000s. Progressive rock/metal peaked twice, once in the late-80s wave (perhaps thanks to Rush), and again the early 2000s as progressive metal started to take shape. Recently progressive rock/metal been the most highly-rated genre after doom metal.

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